Update InternalDocs/garbage_collector.md

Co-authored-by: Alex Waygood <[email protected]>

Author: markshannon

InternalDocs/garbage_collector.md

@@ -613,7 +613,7 @@ tracking status of the object.
       False
       >>> gc.is_tracked([])
       True
-      >>> gc.is_tracked(("a": 1))
+      >>> gc.is_tracked(("a", 1))
       False
       >>> gc.is_tracked({"a": 1})
       True