Stop supporting Python 3.9 #168

Job	Run time
Sign on windows	37s
Sign on macos	29s
Sign on ubuntu	22s
Verify macos bundle on ubuntu	17s
Verify macos bundle on macos	26s
Verify ubuntu bundle on macos	14s
Verify windows bundle on macos	18s
Verify windows bundle on ubuntu	19s
Verify ubuntu bundle on ubuntu	17s
Verify macos bundle on windows	37s
Verify windows bundle on windows	35s
Verify ubuntu bundle on windows	34s
	5m 5s

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