Use Sidekiq::Web.configure for Web UI

[hiemanshu]

This fixes #207, Sidekiq::Web.register is deprecated, and Sidekiq 8 requires .configure to be used.

It also happens to be a nicer API than what currently exists.

[codecov]

Codecov Report

Attention: Patch coverage is 71.42857% with 2 lines in your changes missing coverage. Please review.

Project coverage is 98.30%. Comparing base (11aefdf) to head (06d759d).

Files with missing lines	Patch %	Lines
lib/sidekiq/throttled/web.rb	71.42%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #210      +/-   ##
==========================================
- Coverage   98.71%   98.30%   -0.41%     
==========================================
  Files          19       19              
  Lines         468      473       +5     
  Branches       77       79       +2     
==========================================
+ Hits          462      465       +3     
- Misses          6        8       +2     

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[jeffbax]

Thank you for doing this PR, would love to see it get merged @ixti