chore(from_into): Add missing period in docs

Author: xavdid

exercises/23_conversions/from_into.rs

@@ -39,7 +39,7 @@ impl Default for Person {
 // 5. Extract the other element from the split operation and parse it into a
 //    `usize` as the age.
 // If while parsing the age, something goes wrong, then return the default of
-// Person Otherwise, then return an instantiated Person object with the results
+// Person. Otherwise, then return an instantiated Person object with the results
 
 // I AM NOT DONE