Tests

.github: Explicitly install Postgres in platform tests #560

Job	Run time
test-postgres (9.5)	3m 46s
test-platforms (3.8, ubuntu-latest, asyncio)	3m 15s
test-postgres (9.6)	3m 34s
test-postgres (10)	3m 27s
test-platforms (3.8, ubuntu-latest, uvloop)	3m 30s
test-postgres (11)	3m 40s
test-platforms (3.8, macos-latest, asyncio)	2m 46s
test-postgres (12)	3m 34s
test-platforms (3.8, macos-latest, uvloop)	2m 46s
test-postgres (13)	3m 29s
test-platforms (3.8, windows-latest, asyncio)	11m 7s
test-postgres (14)	3m 27s
test-platforms (3.9, ubuntu-latest, asyncio)	3m 22s
test-postgres (15)	3m 49s
test-platforms (3.9, ubuntu-latest, uvloop)	3m 23s
test-postgres (16)	3m 36s
test-platforms (3.9, macos-latest, asyncio)	2m 19s
test-platforms (3.9, macos-latest, uvloop)	2m 19s
test-platforms (3.9, windows-latest, asyncio)	11m 7s
test-platforms (3.10, ubuntu-latest, asyncio)	3m 9s
test-platforms (3.10, ubuntu-latest, uvloop)	3m 26s
test-platforms (3.10, macos-latest, asyncio)	2m 18s
test-platforms (3.10, macos-latest, uvloop)	2m 18s
test-platforms (3.10, windows-latest, asyncio)	11m 8s
test-platforms (3.11, ubuntu-latest, asyncio)	3m 31s
test-platforms (3.11, ubuntu-latest, uvloop)	3m 21s
test-platforms (3.11, macos-latest, asyncio)	2m 15s
test-platforms (3.11, macos-latest, uvloop)	2m 15s
test-platforms (3.11, windows-latest, asyncio)	10m 55s
test-platforms (3.12, ubuntu-latest, asyncio)	3m 24s
test-platforms (3.12, macos-latest, asyncio)	2m 17s
test-platforms (3.12, windows-latest, asyncio)	11m 8s
Regression Tests	0s
	2h 19m 41s

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