test: deflake test-http-remove-header-stays-removed

[lpinca]

Instead of relying on a timer, verify that socket.end() is called when the 'finish' event is emitted on the ServerResponse object.

[lpinca]

Fixes https://ci.nodejs.org/job/node-test-commit-linux-containered/46445/nodes=ubuntu2204_sharedlibs_shared_x64/testReport/junit/(root)/parallel/test_http_remove_header_stays_removed/

---
duration_ms: 803.619
exitcode: 1
severity: fail
stack: |-
  ok
  node:assert:90
    throw new AssertionError(obj);
    ^

  AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:

  false !== true

      at Timeout._onTimeout (/home/iojs/build/workspace/node-test-commit-linux-containered/test/parallel/test-http-remove-header-stays-removed.js:61:18)
      at listOnTimeout (node:internal/timers:614:17)
      at process.processTimers (node:internal/timers:549:7) {
    generatedMessage: true,
    code: 'ERR_ASSERTION',
    actual: false,
    expected: true,
    operator: 'strictEqual'
  }

  Node.js v23.0.0-pre
...

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.03%. Comparing base (c42d846) to head (673e7ce).
Report is 22 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #55004   +/-   ##
=======================================
  Coverage   88.03%   88.03%           
=======================================
  Files         652      652           
  Lines      183759   183759           
  Branches    35861    35856    -5     
=======================================
+ Hits       161770   161772    +2     
+ Misses      15239    15236    -3     
- Partials     6750     6751    +1     

see 34 files with indirect coverage changes

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/62566/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/62576/