fix(from_str): Correct typos

typos in the comments

exercises/conversions/from_str.rs

@@ -13,13 +13,13 @@ struct Person {
 // I AM NOT DONE
 
 // Steps:
-// 1. If the length of the provided string is 0 an error should be returned
+// 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 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>()`.
-// 5. If while extracting the name and the age something goes wrong an error should be returned
+//    with something like `"4".parse::<usize>()`
+// 5. 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
 
 impl FromStr for Person {