Fix import error on Python 3.10: remove trailing commas in StructuredDataType

[abrignoni]

Six members of StructuredDataType in ccl_mozilla_reader/serialization_formats/ccl_moz_structured_clone_reader.py had a trailing comma after enum.auto(), which turns the value into a tuple. Python 3.11 and newer resolve auto() inside the tuple so it still works there, but Python 3.10 fails as soon as the module is imported:

TypeError: int() argument must be a string, a bytes-like object or a real number, not 'auto'

This PR just removes the six trailing commas (ARRAY_BUFFER_OBJECT_V2, DO_NOT_USE_1, DO_NOT_USE_2, TYPED_ARRAY_OBJECT_V2, DO_NOT_USE_3, DATA_VIEW_OBJECT_V2). I checked that:

• all 98 enum values are exactly the same before and after on Python 3.12
• the class now loads fine on Python 3.10

I ran into this through mister_skinnylegs, which ALEAPP uses. The import failure on Python 3.10 made me disable the browser artifact plugins there (abrignoni/ALEAPP#976). Since #2 set requires-python to >=3.10, this small fix makes 3.10 actually work.

Thanks for these tools!