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

exercises/conversions/from_str.rs

@@ -1,10 +1,13 @@
 // from_str.rs
-// This is similar to from_into.rs, but this time we'll implement `FromStr`
-// and return errors instead of falling back to a default value.
-// Additionally, upon implementing FromStr, you can use the `parse` method
-// on strings to generate an object of the implementor type.
-// You can read more about it at https://doc.rust-lang.org/std/str/trait.FromStr.html
-// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a hint.
+//
+// This is similar to from_into.rs, but this time we'll implement `FromStr` and
+// return errors instead of falling back to a default value. Additionally, upon
+// implementing FromStr, you can use the `parse` method on strings to generate
+// an object of the implementor type. You can read more about it at
+// https://doc.rust-lang.org/std/str/trait.FromStr.html
+//
+// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a
+// hint.
 
 use std::num::ParseIntError;
 use std::str::FromStr;
@@ -33,15 +36,18 @@ enum ParsePersonError {
 // Steps:
 // 1. If the length of the provided string is 0, an error should be returned
 // 2. Split the given string on the commas present in it
-// 3. Only 2 elements should be returned from the split, otherwise return an error
+// 3. Only 2 elements should be returned from the split, otherwise return an
+//    error
 // 4. Extract the first element from the split operation and use it as the name
-// 5. Extract the other element from the split operation and parse it into a `usize` as the age
-//    with something like `"4".parse::<usize>()`
-// 6. If while extracting the name and the age something goes wrong, an error should be returned
+// 5. Extract the other element from the split operation and parse it into a
+//    `usize` as the age with something like `"4".parse::<usize>()`
+// 6. If while extracting the name and the age something goes wrong, an error
+//    should be returned
 // If everything goes well, then return a Result of a Person object
 //
-// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if you want to return a
-// string error message, you can do so via just using return `Err("my error message".into())`.
+// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if
+// you want to return a string error message, you can do so via just using
+// return `Err("my error message".into())`.
 
 impl FromStr for Person {
     type Err = ParsePersonError;