MNT: drop deprecated License classifier, update related metadata (PEP 639) #276

Job	Run time
tests / Load tox environments	9s
tests / codestyle (ubuntu-latest)	19s
tests / py39-test-pytest53 (ubuntu-latest)	50s
tests / py310-test-pytest61 (windows-latest)	1m 11s
tests / py39-test-pytestoldest (windows-latest)	1m 20s
tests / py312-test-pytest73 (macos-latest)	39s
tests / py311-test-pytest71 (windows-latest)	1m 26s
tests / py313-test-pytest74 (windows-latest)	1m 18s
tests / py310-test-pytest60 (macos-latest)	44s
tests / py311-test-pytest62 (ubuntu-latest)	46s
tests / py311-test-pytest70 (macos-latest)	36s
tests / py313-test-devdeps (ubuntu-latest)	1m 33s
tests / py314-test-pytest90 (ubuntu-latest)	48s
tests / py312-test-pytest72 (ubuntu-latest)	37s
publish	0s
	12m 16s

Provide feedback