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

GitOrigin-RevId: 4cd6ca102a94e1b64ba3f940cc26b4d7b2b82964
diff --git a/include/tuple b/include/tuple
index 61ff212..2b11a3f 100644
--- a/include/tuple
+++ b/include/tuple
@@ -1509,4 +1509,4 @@
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif  // _LIBCPP_TUPLE
+#endif // _LIBCPP_TUPLE