chore: Fix a couple broken book links

exercises/primitive_types/primitive_types5.rs

@@ -39,7 +39,7 @@ fn main() {
 
 
 // Take a look at 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
-// Particularly the part about destructuring (second to last example in the section). 
+// https://doc.rust-lang.org/book/ch03-02-data-types.html#the-tuple-type
+// Particularly the part about destructuring (second to last example in the section).
 // You'll need to make a pattern to bind `name` and `age` to the appropriate parts
 // of the tuple. You can do it!!

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
+// https://doc.rust-lang.org/book/ch03-02-data-types.html#the-tuple-type
 // Now you have another tool in your toolbox!