docs: improve language in control-flow-basics section (#2887)

I asked Gemini to review the English for inconsistencies and grammar
mistakes. This is the result and I hope it's useful!

As a non-native speaker, it is hard for me to evaluate the finer
details, so let me know if you would like to see changes (or even
better: make them directly in the PR with the suggestion function).

---------

Co-authored-by: Dmitri Gribenko <gribozavr@gmail.com>

src/control-flow-basics/blocks-and-scopes.md

@@ -4,9 +4,8 @@ minutes: 5
 
 # Blocks and Scopes
 
-A block in Rust contains a sequence of expressions, enclosed by braces `{}`.
-Each block has a value and a type, which are those of the last expression of the
-block:
+A block in Rust contains a sequence of expressions, enclosed by braces {}. The
+final expression of a block determines the value and type of the whole block:
 
 ```rust,editable
 fn main() {

src/control-flow-basics/break-continue.md

@@ -30,7 +30,7 @@ fn main() {
 
 <details>
 
-Note that `loop` is the only looping construct which can return a non-trivial
+Note that `loop` is the only looping construct that can return a non-trivial
 value. This is because it's guaranteed to only return at a `break` statement
 (unlike `while` and `for` loops, which can also return when the condition
 fails).

src/control-flow-basics/break-continue/labels.md

@@ -1,7 +1,7 @@
 # Labels
 
-Both `continue` and `break` can optionally take a label argument which is used
-to break out of nested loops:
+Both `continue` and `break` can optionally take a label argument that is used to
+break out of nested loops:
 
 ```rust,editable
 fn main() {

src/control-flow-basics/exercise.md

@@ -22,7 +22,7 @@ For example, beginning with _n<sub>1</sub>_ = 3:
 - 2 is even, so _n<sub>8</sub>_ = 1; and
 - the sequence terminates.
 
-Write a function to calculate the length of the collatz sequence for a given
+Write a function to calculate the length of the Collatz sequence for a given
 initial `n`.
 
 ```rust,editable,should_panic

src/control-flow-basics/loops/loop.md

@@ -19,6 +19,6 @@ fn main() {
 <details>
 
 - The `loop` statement works like a `while true` loop. Use it for things like
-  servers which will serve connections forever.
+  servers that will serve connections forever.
 
 </details>

src/control-flow-basics/match.md

@@ -59,7 +59,7 @@ fn main() {
 ## More to Explore
 
 - To further motivate the usage of `match`, you can compare the examples to
-  their equivalents written with `if`. In the second case matching on a `bool`
+  their equivalents written with `if`. In the second case, matching on a `bool`,
   an `if {} else {}` block is pretty similar. But in the first example that
   checks multiple cases, a `match` expression can be more concise than
   `if {} else if {} else if {} else`.