Remove `schedule_during_release_override`, which is no longer used. #227

Job	Run time
collect_tests	5s
test-common-packages (packages/cocoon_server)	28s
test-common-packages (packages/cocoon_common)	25s
test-common-packages (packages/buildbucket-dart)	29s
test-common-packages (dev/cocoon_code_health)	21s
test-common-packages (dev/githubanalysis)	18s
test-common-packages (packages/cocoon_common_test)	23s
test-common-packages (packages/cocoon_server_test)	29s
test-common-packages (cipd_packages/device_doctor)	28s
test-common-packages (cipd_packages/codesign)	22s
test-common-packages (auto_submit)	36s
test-common-packages (licenses)	15s
	4m 39s

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