meta: [sentry-sidekiq] README.md: Drop broken Dependabot version compatibility badge

[olleolleolle]

The README badge list ended with a now-defunct one, from Dependabot. This PR removes it, without a replacement.

I didn't go through each neighboring gem's README for the same issue.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.61%. Comparing base (7d10c02) to head (8b55084).
⚠️ Report is 150 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3042      +/-   ##
==========================================
+ Coverage   90.13%   90.61%   +0.48%     
==========================================
  Files         132      148      +16     
  Lines        5301     5915     +614     
==========================================
+ Hits         4778     5360     +582     
- Misses        523      555      +32     

Components	Coverage Δ
sentry-ruby	97.31% <ø> (+0.02%)	⬆️
sentry-rails	58.42% <ø> (+2.91%)	⬆️
sentry-sidekiq	95.84% <ø> (+0.79%)	⬆️
sentry-resque	94.44% <ø> (ø)
sentry-delayed_job	94.68% <ø> (ø)
sentry-opentelemetry	99.56% <100.00%> (+0.25%)	⬆️
see 45 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.