upgrade flake8 (#1040) #649

Job	Run time
coverage	4m 21s
lint	2m 23s
docs	3m 32s
Rust unit tests (ubuntu-latest)	6m 25s
Rustfmt	19s
Rust unit tests (macos-latest)	3m 3s
test (macos-latest, 3.8)	6m 51s
typecheck	1m 58s
Rust unit tests (windows-latest)	4m 39s
test (macos-latest, 3.9)	9m 31s
test (macos-latest, 3.10)	7m 16s
test (macos-latest, 3.11)	8m 2s
test (macos-latest, 3.12-dev)	10m 23s
test (ubuntu-latest, 3.8)	2m 32s
test (ubuntu-latest, 3.9)	4m 28s
test (ubuntu-latest, 3.10)	4m 38s
test (ubuntu-latest, 3.11)	5m 43s
test (ubuntu-latest, 3.12-dev)	6m 3s
test (windows-latest, 3.8)	6m 55s
test (windows-latest, 3.9)	7m 57s
test (windows-latest, 3.10)	9m 17s
test (windows-latest, 3.11)	10m 42s
test (windows-latest, 3.12-dev)	11m 2s
	2h 18m 0s

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