fix(exercises): remove trailing spaces

exercises/macros/README.md

@@ -4,7 +4,7 @@ Rust's macro system is very powerful, but also kind of difficult to wrap your
 head around. We're not going to teach you how to write your own fully-featured
 macros. Instead, we'll show you how to use and create them.
 
-If you'd like to learn more about writing your own macros, the 
+If you'd like to learn more about writing your own macros, the
 [macrokata](https://github.com/tfpk/macrokata) project has a similar style
 of exercises to Rustlings, but is all about learning to write Macros.