Third-party stubs: import from collections.abc where possible (#7637)

stubs/xmltodict/xmltodict.pyi

@@ -1,6 +1,7 @@
 from _typeshed import SupportsRead, SupportsWrite
 from collections import OrderedDict
-from typing import Any, Mapping, overload
+from collections.abc import Mapping
+from typing import Any, overload
 
 class ParsingInterrupted(Exception): ...