Pin Ubuntu to 22.04 for Galaxy releases using Python 3.7 #304

Job	Run time
test (ubuntu-latest, py38, dev, 3.8)	46s
test (ubuntu-latest, py38, release_24.1, 3.8)	36s
test (ubuntu-latest, py38, release_24.0, 3.8)	33s
test (ubuntu-22.04, py38, release_23.2, 3.7)	33s
test (ubuntu-22.04, py38, release_23.1, 3.7)	35s
test (ubuntu-22.04, py38, release_23.0, 3.7)	46s
test (ubuntu-22.04, py38, release_22.05, 3.7)	46s
test (ubuntu-22.04, py38, release_22.01, 3.7)	47s
test (ubuntu-22.04, py38, release_21.09, 3.7)	46s
test (ubuntu-22.04, py38, release_21.05, 3.7)	47s
test (ubuntu-22.04, py38, release_21.01, 3.7)	46s
test (ubuntu-22.04, py38, release_20.09, 3.7)	47s
test (ubuntu-22.04, py38, release_20.05, 3.7)	47s
test (ubuntu-22.04, py38, release_20.01, 3.7)	47s
test (ubuntu-22.04, py38, release_19.09, 3.7)	47s
test (ubuntu-22.04, py38, release_19.05, 3.7)	46s
test (ubuntu-latest, py313, dev, 3.8)	35s
	12m 10s

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