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

exercises/generics/generics1.rs

@@ -1,7 +1,10 @@
-// This shopping list program isn't compiling!
-// Use your knowledge of generics to fix it.
-
-// Execute `rustlings hint generics1` or use the `hint` watch subcommand for a hint.
+// generics1.rs
+//
+// This shopping list program isn't compiling! Use your knowledge of generics to
+// fix it.
+//
+// Execute `rustlings hint generics1` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE
 

exercises/generics/generics2.rs

@@ -1,7 +1,10 @@
+// generics2.rs
+//
 // This powerful wrapper provides the ability to store a positive integer value.
 // Rewrite it using generics so that it supports wrapping ANY type.
-
-// Execute `rustlings hint generics2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint generics2` or use the `hint` watch subcommand for a
+// hint.
 
 // I AM NOT DONE