Very minor grammatical fix in a comment.

Python/import.c

@@ -1029,7 +1029,7 @@ is_builtin(char *name)
 
 /* Return an importer object for a sys.path/pkg.__path__ item 'p',
    possibly by fetching it from the path_importer_cache dict. If it
-   wasn't yet cached, traverse path_hooks until it a hook is found
+   wasn't yet cached, traverse path_hooks until a hook is found
    that can handle the path item. Return None if no hook could;
    this tells our caller it should fall back to the builtin
    import mechanism. Cache the result in path_importer_cache.