Bump crossbeam-epoch from 0.9.18 to 0.9.20

[cakebaker]

Fixes #97

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.07%. Comparing base (3f5db7d) to head (1c780cf).
⚠️ Report is 47 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #98      +/-   ##
==========================================
+ Coverage   78.64%   85.07%   +6.42%     
==========================================
  Files          13       15       +2     
  Lines        2585     3490     +905     
  Branches      230      246      +16     
==========================================
+ Hits         2033     2969     +936     
+ Misses        552      520      -32     
- Partials        0        1       +1     

Flag	Coverage Δ
macos_latest	84.95% <ø> (+7.31%)	⬆️
ubuntu_latest	84.55% <ø> (+6.37%)	⬆️
windows_latest	17.33% <ø> (+2.63%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[codspeed-hq]

Merging this PR will not alter performance

✅ 20 untouched benchmarks
⏩ 9 skipped benchmarks¹

---

_{Comparing cakebaker:bump_crossbeam_epoch (1c780cf) with main (b19bff4)}

Footnotes

1. 9 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩