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

GitOrigin-RevId: 4cd6ca102a94e1b64ba3f940cc26b4d7b2b82964
diff --git a/include/string.h b/include/string.h
index e09251d..2d56344 100644
--- a/include/string.h
+++ b/include/string.h
@@ -106,4 +106,4 @@
 }
 #endif
 
-#endif  // _LIBCPP_STRING_H
+#endif // _LIBCPP_STRING_H