feat(generics): add hint comments

exercises/generics/generics1.rs

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

exercises/generics/generics2.rs

@@ -1,7 +1,7 @@
 // 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` for hints!
+// Execute `rustlings hint generics2` or use the `hint` watch subcommand for a hint.
 
 // I AM NOT DONE