Expand version pins to support sidekiq 8.0

[bmulholland]

Not sure if you all want update PRs, considering issues are closed. Still, this is currently the most updated version of simplekiq and we've been using it -- thank you -- so this is a small way to give back.

[CLAassistant]

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[Farjaad]

thanks for submitting this PR (and sorry for taking so long to reply)! can you please accept the Contributor License Agreement we can merge this

[Farjaad]

closing in favour of #17 where we added some tests as well.

thanks again for submitting this PR!

[bmulholland]

Apologies for the slow response. Your PR is better anyway, so I'm happy to have this closed.

Thanks again for publishing your work, so we can use it!