[libc++] NFC: Normalize `#endif //` comment indentation

GitOrigin-RevId: 4cd6ca102a94e1b64ba3f940cc26b4d7b2b82964
diff --git a/include/shared_mutex b/include/shared_mutex
index 5448d8a..72a0ffa 100644
--- a/include/shared_mutex
+++ b/include/shared_mutex
@@ -500,10 +500,10 @@
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif  // !_LIBCPP_HAS_NO_THREADS
+#endif // !_LIBCPP_HAS_NO_THREADS
 
-#endif  // _LIBCPP_STD_VER > 11
+#endif // _LIBCPP_STD_VER > 11
 
 _LIBCPP_POP_MACROS
 
-#endif  // _LIBCPP_SHARED_MUTEX
+#endif // _LIBCPP_SHARED_MUTEX