Fix events remove listener emission

[Han5991]

Description

This PR fixes a bug where the removeListener event was not being emitted when the last listener was removed from an EventEmitter.

Background

When removeListener() is called and the last listener is removed (_eventsCount === 0), the code path that emits the removeListener event
was being skipped. This was because the emission logic was inside the else block of the event count check.

This issue particularly affects once() listeners, which automatically call removeListener() after execution. If the once listener was the
last listener, the removeListener event would not fire.

Changes

• lib/events.js: Moved the removeListener event emission outside the conditional block to ensure it always executes when a listener is
  removed
• test/parallel/test-event-emitter-remove-listeners.js: Added test coverage for once() listeners with removeListener event monitoring

Test Plan

./node test/parallel/test-event-emitter-remove-listeners.js
make test-ci

All tests pass, including the new test case that verifies removeListener events are emitted when once() listeners are automatically removed.

Checklist

- tests are included
- documentation is not affected
- make -j4 test passes locally

Related Issues

fixes: #59977

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.53%. Comparing base (bfc81ca) to head (d322e4d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #60137      +/-   ##
==========================================
- Coverage   88.55%   88.53%   -0.02%     
==========================================
  Files         704      704              
  Lines      208087   208088       +1     
  Branches    40019    40014       -5     
==========================================
- Hits       184266   184233      -33     
- Misses      15818    15862      +44     
+ Partials     8003     7993      -10     

Files with missing lines	Coverage Δ
lib/events.js	99.83% <100.00%> (+<0.01%)	⬆️

... and 25 files with indirect coverage changes

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