fmt fixes

library/std/src/sync/nonpoison/mutex.rs

@@ -10,7 +10,7 @@ use crate::ptr::NonNull;
 use crate::sys::sync as sys;
 
 /// A mutual exclusion primitive useful for protecting shared data.
-/// 
+///
 /// For more information about mutexes, check out the documentation for the
 /// poisoning variant of this lock found at [std::sync::poison::Mutex](std::sync::Mutex).
 ///