Fix CI #19

Job	Run time
publish / Build source and wheel distribution	52s
tests / Load tox environments	5s
tests / codestyle (ubuntu-latest)	28s
tests / py38-test-mpl33 (ubuntu-latest)	34s
tests / py39-test-mpl34 (ubuntu-latest)	32s
tests / py39-test-mpl35 (ubuntu-latest)	41s
tests / py310-test-mpl36 (ubuntu-latest)	43s
tests / py310-test-mpl37 (ubuntu-latest)	44s
tests / py311-test-mpldev (ubuntu-latest)	1m 38s
tests / py38-test-mpl33 (windows-latest)	1m 39s
tests / py39-test-mpl34 (macos-12)	1m 12s
tests / py39-test-mpl35 (windows-latest)	1m 36s
tests / py310-test-mpl36 (macos-latest)	46s
tests / py310-test-mpl37 (windows-latest)	2m 22s
tests / py311-test-mpldev (windows-latest)	3m 58s
tests / py311-test-mpl38-image (ubuntu-latest)	14s
	18m 4s

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