chore: Clean up some formatting in exercises

exercises/primitive_types/primitive_types6.rs

@@ -38,8 +38,8 @@ fn main() {
 
 
 
-// While you could use a destructuring `let` for the tuple here, try 
-// indexing into it instead, as explained in the last example of the 
+// While you could use a destructuring `let` for the tuple here, try
+// indexing into it instead, as explained in the last example of the
 // Data Types -> The Tuple Type section of the book:
 // https://doc.rust-lang.org/stable/book/ch03-02-data-types.html#the-tuple-type
 // Now you have another tool in your toolbox!