Fixup the spec string for sys.executable #3933

Job	Run time
tox env type on ubuntu-latest	39s
test 3.12 on ubuntu-latest	4m 30s
tox env type on windows-latest	1m 13s
tox env dev on ubuntu-latest	40s
test 3.12 on windows-latest	11m 16s
tox env dev on windows-latest	1m 8s
test 3.12 on macos-latest	4m 46s
tox env docs on ubuntu-latest	4m 37s
test 3.11 on ubuntu-latest	3m 8s
tox env pkg_meta on ubuntu-latest	25s
test 3.11 on windows-latest	10m 7s
test 3.11 on macos-latest	3m 55s
test 3.10 on ubuntu-latest	3m 22s
test 3.10 on windows-latest	11m 24s
test 3.10 on macos-latest	4m 1s
test 3.9 on ubuntu-latest	3m 14s
test 3.9 on windows-latest	10m 38s
test 3.9 on macos-latest	4m 2s
test 3.8 on ubuntu-latest	3m 17s
test 3.8 on windows-latest	10m 38s
test 3.8 on macos-latest	4m 31s
	1h 41m 31s

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