Clean up and unify exercises

exercises/13_error_handling/errors1.rs

@@ -1,13 +1,8 @@
-// errors1.rs
-//
 // This function refuses to generate text to be printed on a nametag if you pass
 // it an empty string. It'd be nicer if it explained what the problem was,
 // instead of just sometimes returning `None`. Thankfully, Rust has a similar
 // construct to `Option` that can be used to express error conditions. Let's use
 // it!
-//
-// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a
-// hint.
 
 fn main() {
     // You can optionally experiment here.