adjust timing tests #88

Job	Run time
ci (tpb, ubuntu-22.04, --pb --threads --enable-libffi, test-some-fast)	29m 22s
ci (a6osx, macos-12)	15m 0s
ci (ta6osx, macos-12)	21m 6s
ci (i3le, ubuntu-22.04)	12m 37s
ci (ti3le, ubuntu-22.04)	16m 10s
ci (a6le, ubuntu-22.04)	8m 52s
ci (ta6le, ubuntu-22.04)	12m 5s
ci (ta6le, ubuntu-22.04, reboot, -m=ta6le --force, re.boot SCHEME="chezscheme", test-some-fast)	8m 25s
ci (i3nt, windows-2022, vs)	11m 28s
ci (ti3nt, windows-2022, vs)	14m 27s
ci (a6nt, windows-2022, vs)	12m 39s
ci (ta6nt, windows-2022, vs)	15m 23s
ci (ta6nt, windows-2022, gcc)	12m 49s
	3h 10m 23s

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