docs: cleanup the explanation paragraphs at the start of each exercise.

exercises/enums/enums1.rs

@@ -1,4 +1,5 @@
 // enums1.rs
+//
 // No hints this time! ;)
 
 // I AM NOT DONE

exercises/enums/enums2.rs

@@ -1,5 +1,7 @@
 // enums2.rs
-// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/enums/enums3.rs

@@ -1,6 +1,9 @@
 // enums3.rs
+//
 // Address all the TODOs to make the tests pass!
-// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 
@@ -37,8 +40,10 @@ impl State {
     }
 
     fn process(&mut self, message: Message) {
-        // TODO: create a match expression to process the different message variants
-        // Remember: When passing a tuple as a function argument, you'll need extra parentheses: fn function((t, u, p, l, e))
+        // TODO: create a match expression to process the different message
+        // variants
+        // Remember: When passing a tuple as a function argument, you'll need
+        // extra parentheses: fn function((t, u, p, l, e))
     }
 }