Use dbg! instead of println! in Day 1 mng session (#2652)

As mentioned in #2478, this cleans up the code blocks when all that is
needed is a trivial debug print statement.
Only making changes to Day 1 morning session so that I can get feedback
before proceeding with the rest of the course.

---------

Co-authored-by: Eric Githinji <egithinji@google.com>

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

@@ -23,7 +23,7 @@ fn main() {
         if i % 2 == 0 {
             continue;
         }
-        println!("{}", i);
+        dbg!(i);
     }
 }
 ```