ci: run windows tests with a single worker #270

Job	Run time
downgrade (1.10, core)	16m 10s
downgrade (1.10, downstream)	8m 34s
test (core, 1.10, ubuntu-latest)	16m 6s
downgrade (1.10, wrappers)	10m 11s
test (core, 1.10, macos-latest)	14m 43s
test (core, 1.10, windows-latest)	25m 37s
test (core, 1, ubuntu-latest)	27m 48s
test (core, 1, macos-latest)	18m 31s
test (core, 1, windows-latest)	40m 57s
test (downstream, 1.10, ubuntu-latest)	7m 55s
test (downstream, 1.10, macos-latest)	6m 3s
test (downstream, 1.10, windows-latest)	10m 43s
test (downstream, 1, ubuntu-latest)	17m 13s
test (downstream, 1, macos-latest)	10m 12s
test (downstream, 1, windows-latest)	21m 30s
test (wrappers, 1.10, ubuntu-latest)	9m 32s
test (wrappers, 1.10, macos-latest)	6m 57s
test (wrappers, 1.10, windows-latest)	12m 37s
test (wrappers, 1, ubuntu-latest)	19m 19s
test (wrappers, 1, macos-latest)	10m 47s
test (wrappers, 1, windows-latest)	23m 40s
	5h 35m 5s

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