Clean up and unify exercises

exercises/12_options/options1.rs

@@ -1,8 +1,3 @@
-// options1.rs
-//
-// Execute `rustlings hint options1` or use the `hint` watch subcommand for a
-// hint.
-
 // This function returns how much icecream there is left in the fridge.
 // If it's before 10PM, there's 5 scoops left. At 10PM, someone eats it
 // all, so there'll be no more left :(

exercises/12_options/options2.rs

@@ -1,8 +1,3 @@
-// options2.rs
-//
-// Execute `rustlings hint options2` or use the `hint` watch subcommand for a
-// hint.
-
 fn main() {
     // You can optionally experiment here.
 }

exercises/12_options/options3.rs

@@ -1,8 +1,3 @@
-// options3.rs
-//
-// Execute `rustlings hint options3` or use the `hint` watch subcommand for a
-// hint.
-
 struct Point {
     x: i32,
     y: i32,