Update library/alloc/src/string.rs

Author: jonhoo

library/alloc/src/string.rs

@@ -1972,7 +1972,7 @@ impl String {
     /// so the leaked allocation may include unused capacity that is not part
     /// of the returned slice. The advantage of this is that it avoids the potential
     /// reallocation that [`shrink_to_fit`] may perform.
-    /// 
+    ///
     /// If you want to discard excess capacity, call [`into_boxed_str`],
     /// and then [`Box::leak`] instead.
     ///