Use non-deprecated form of Redis.sadd/srem

[irvingreid]

This fixes the deprecation warnings for Redis#sadd and Redis#srem output by version 4.8 of redis-rb, following the example of the changes made to Resque in resque/resque#1827

Other tests failed when upgrading redis-rb to 5.0.4, which is why I added the restriction to resque-scheduler.gemspec

To avoid future regressions, I enabled Redis.raise_deprecations = true so that the test suite is more likely to catch future Redis deprecations.

[irvingreid]

Looks like your test matrix pairs Redis 4.8 with older versions of the resque gem, which trigger deprecation failures. Would you rather change the test matrix, or remove Redis.raise_deprecations = true?

[irvingreid]

@PatrickTulskie removed the gemspec change here too, because the main branch fixed Redis 5.0 compatibility :-)

[carlwiedemann]

Friendly bump. Is there anything preventing this from getting merged?