bump: min Python 3.9 #947

Job	Run time
check-md-links-w-config / markdown-link-check	26s
check-docs / make-docs (html)	2m 44s
check-md-links-default / markdown-link-check	12s
check-docs / make-docs (doctest)	1m 44s
check-docs / make-docs (linkcheck)	1m 43s
check-package / init-store	11s
check-package-extras / init-store	5s
check-precommit / pre-commit	17s
check-schema-fixed / schema	16s
check-schema-latest / schema	13s
check-typing / mypy	17s
check-package-extras / pkg-build (ubuntu-latest)	16s
check-package / pkg-build (ubuntu-22.04, 3.10)	16s
check-schema	1s
check-package-extras / pkg-check (ubuntu-22.04, 3.10)	24s
check-package-extras / pkg-check (macos-13, 3.10)	33s
check-package-extras / pkg-check (windows-2022, 3.10)	1m 1s
check-package / pkg-check (ubuntu-22.04, 3.9)	13s
check-package / pkg-check (ubuntu-22.04, 3.12)	15s
check-package / pkg-check (macos-13, 3.9)	23s
check-package / pkg-check (macos-13, 3.12)	25s
check-package / pkg-check (windows-2022, 3.9)	51s
check-package / pkg-check (windows-2022, 3.12)	43s
check-package / pkg-guardian	1s
check-package-extras / pkg-guardian	1s
	13m 31s

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