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

exercises/if/if1.rs

@@ -1,4 +1,5 @@
 // if1.rs
+//
 // Execute `rustlings hint if1` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE

exercises/if/if2.rs

@@ -1,7 +1,8 @@
 // if2.rs
-
+//
 // Step 1: Make me compile!
 // Step 2: Get the bar_for_fuzz and default_to_baz tests passing!
+//
 // Execute `rustlings hint if2` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE