test: python E721 and flake8 updates #28194

Update our functional tests per E721 enforced by flake8 6.1.0, and update our CI lint task to use that release. This makes the following linter output on current master with flake8 6.1.0 green.

$ ./test/lint/lint-python.py ; ./test/lint/lint-spelling.py 
test/functional/p2p_invalid_locator.py:35:16: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`
test/functional/test_framework/siphash.py:34:12: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`
test/functional/test_framework/siphash.py:64:12: E721 do not compare types, for exact checks use `is` / `is not`, for instance checks use `isinstance()`
src/test/fuzz/descriptor_parse.cpp:88: occurences ==> occurrences
^ Warning: codespell identified likely spelling errors. Any false positives? Add them to the list of ignored words in test/lint/spelling.ignore-words.txt

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CI lint task report looks good https://cirrus-ci.com/task/6522164438892544.

lgtm ACK bee2d57a655645dbfaf0242e85c5af034023a2fb