Documentation incorrect for delete_by_digest

[tanner-rutgers]

Describe the bug
The documentation here says we can call SidekiqUniqueJobs::Digests.delete_by_digest(digest) to clean up dead locks on job death. However, that method appears to be an instance method, not a class method.

Expected behavior
I believe the real call should be SidekiqUniqueJobs::Digests.new.delete_by_digest(digest)

Current behavior
NoMethodError · undefined method `delete_by_digest' for SidekiqUniqueJobs::Digests:Class

Additional context

Version: 7.0.0.beta25

[mhenrixon]

I think a convenience class method would be a good idea here but I'll look into it

[mhenrixon]

Ok, updating README seems like a better option in this case! done in cffe931