perf: remove unnecessary lock

[noneback]

Since RC ref strictly happens before deref, while tasks are scheduling and executing, and go mem order is the same as seq, so that the locks can be removed.

https://go.dev/ref/mem#atomic

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.81%. Comparing base (ffb137c) to head (7cae748).
Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #93      +/-   ##
==========================================
+ Coverage   84.24%   85.81%   +1.57%     
==========================================
  Files          13       13              
  Lines         711      677      -34     
==========================================
- Hits          599      581      -18     
+ Misses         87       76      -11     
+ Partials       25       20       -5     

Flag	Coverage Δ
unittests	85.81% <100.00%> (+1.57%)	⬆️

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

☔ View full report in Codecov by Sentry.
📢 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.