vi: control-flow-basics/excercise.md translations (#2112)

I think the msg in the file maybe out of sync with
https://google.github.io/comprehensive-rust/control-flow-basics/exercise.html.

Should I continue to refer to the .po file as a source-of-truth, or
should I update the English message, as well as the Vietnamese
translation in this file?

Or should we re-sync the vi.po file first?

po/vi.po

@@ -3694,168 +3694,172 @@ msgid ""
 "The [Collatz Sequence](https://en.wikipedia.org/wiki/Collatz_conjecture) is "
 "defined as follows, for an arbitrary n"
 msgstr ""
+"[Chuỗi Collatz](https://vi.wikipedia.org/wiki/"
+"Gi%E1%BA%A3_thuy%E1%BA%BFt_Collatz) được định nghĩa như sau: với một giá trị "
+"bất kì n"
 
 #: src/control-flow-basics/exercise.md
 msgid "1"
-msgstr ""
+msgstr "1"
 
 #: src/control-flow-basics/exercise.md
 msgid " greater than zero:"
-msgstr ""
+msgstr " lớn hơn 0:"
 
 #: src/control-flow-basics/exercise.md
 msgid "If _n"
-msgstr ""
+msgstr "Nếu _n"
 
 #: src/control-flow-basics/exercise.md
 msgid "i"
-msgstr ""
+msgstr "i"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ is 1, then the sequence terminates at _n"
-msgstr ""
+msgstr "_ là 1, thì chuỗi sẽ chấm dứt tại _n"
 
 #: src/control-flow-basics/exercise.md
 msgid "_."
-msgstr ""
+msgstr "_."
 
 #: src/control-flow-basics/exercise.md
 msgid "_ is even, then _n"
-msgstr ""
+msgstr "_ là chẵn, thì _n"
 
 #: src/control-flow-basics/exercise.md
 msgid "i+1"
-msgstr ""
+msgstr "i+1"
 
 #: src/control-flow-basics/exercise.md
 msgid " = n"
-msgstr ""
+msgstr " = n"
 
 #: src/control-flow-basics/exercise.md
 msgid " / 2_."
-msgstr ""
+msgstr " / 2_."
 
 #: src/control-flow-basics/exercise.md
 msgid "_ is odd, then _n"
-msgstr ""
+msgstr "_ là lẻ, thì _n"
 
 #: src/control-flow-basics/exercise.md
 msgid " = 3 * n"
-msgstr ""
+msgstr " = 3 * n"
 
 #: src/control-flow-basics/exercise.md
 msgid " + 1_."
-msgstr ""
+msgstr " + 1_."
 
 #: src/control-flow-basics/exercise.md
 msgid "For example, beginning with _n"
-msgstr ""
+msgstr "Ví dụ, bắt đầu bằng _n"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ = 3:"
-msgstr ""
+msgstr "_ = 3:"
 
 #: src/control-flow-basics/exercise.md
 msgid "3 is odd, so _n"
-msgstr ""
+msgstr "3 là số lẻ, nên _n"
 
 #: src/control-flow-basics/exercise.md
 msgid "2"
-msgstr ""
+msgstr "2"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ = 3 * 3 + 1 = 10;"
-msgstr ""
+msgstr "_ = 3 * 3 + 1 = 10;"
 
 #: src/control-flow-basics/exercise.md
 msgid "10 is even, so _n"
-msgstr ""
+msgstr "10 là số chẵn, nên _n"
 
 #: src/control-flow-basics/exercise.md src/bare-metal/aps/better-uart.md
 msgid "3"
-msgstr ""
+msgstr "3"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ = 10 / 2 = 5;"
-msgstr ""
+msgstr "_ = 10 / 2 = 5;"
 
 #: src/control-flow-basics/exercise.md
 msgid "5 is odd, so _n"
-msgstr ""
+msgstr "5 là số lẻ, nên _n"
 
 #: src/control-flow-basics/exercise.md src/bare-metal/aps/better-uart.md
 msgid "4"
-msgstr ""
+msgstr "4"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ = 3 * 5 + 1 = 16;"
-msgstr ""
+msgstr "_ = 3 * 5 + 1 = 16;"
 
 #: src/control-flow-basics/exercise.md
 msgid "16 is even, so _n"
-msgstr ""
+msgstr "16 là số chẵn, nên _n"
 
 #: src/control-flow-basics/exercise.md
 msgid "5"
-msgstr ""
+msgstr "5"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ = 16 / 2 = 8;"
-msgstr ""
+msgstr "_ = 16 / 2 = 8;"
 
 #: src/control-flow-basics/exercise.md
 msgid "8 is even, so _n"
-msgstr ""
+msgstr "8 là số chẵn, nên _n"
 
 #: src/control-flow-basics/exercise.md src/bare-metal/aps/better-uart.md
 msgid "6"
-msgstr ""
+msgstr "6"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ = 8 / 2 = 4;"
-msgstr ""
+msgstr "_ = 8 / 2 = 4;"
 
 #: src/control-flow-basics/exercise.md
 msgid "4 is even, so _n"
-msgstr ""
+msgstr "4 là số chẵn, nên _n"
 
 #: src/control-flow-basics/exercise.md
 msgid "7"
-msgstr ""
+msgstr "7"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ = 4 / 2 = 2;"
-msgstr ""
+msgstr "_ = 4 / 2 = 2;"
 
 #: src/control-flow-basics/exercise.md
 msgid "2 is even, so _n"
-msgstr ""
+msgstr "2 là số chẵn, nên _n"
 
 #: src/control-flow-basics/exercise.md src/bare-metal/aps/better-uart.md
 msgid "8"
-msgstr ""
+msgstr "8"
 
 #: src/control-flow-basics/exercise.md
 msgid "_ = 1; and"
-msgstr ""
+msgstr "_ = 1; và"
 
 #: src/control-flow-basics/exercise.md
 msgid "the sequence terminates."
-msgstr ""
+msgstr "chuỗi chấm dứt."
 
 #: src/control-flow-basics/exercise.md
 msgid ""
 "Write a function to calculate the length of the collatz sequence for a given "
 "initial `n`."
 msgstr ""
+"Viết một hàm để tính độ dài chủa chuỗi Collatz với một giá trị ban đầu `n`"
 
 #: src/control-flow-basics/exercise.md src/control-flow-basics/solution.md
 msgid "/// Determine the length of the collatz sequence beginning at `n`.\n"
-msgstr ""
+msgstr "/// Đưa ra độ dài của chuỗi Collatz bắt đầu bằng `n`.\n"
 
 #: src/control-flow-basics/solution.md src/concurrency/threads/scoped.md
 msgid "\"Length: {}\""
-msgstr ""
+msgstr "\"Độ dài: {}\""
 
 #: src/welcome-day-1-afternoon.md src/welcome-day-2-afternoon.md
 #: src/welcome-day-3-afternoon.md src/welcome-day-4-afternoon.md