test: replace deprecated regex test assertions in http trailers test

[cruzz77]

This PR updates test/parallel/test-http-set-trailers.js to align with the recent test modernization work happening across the Node.js codebase. Maintainers have been gradually replacing older assert.ok(/regex/.test(...)) patterns with clearer, more explicit helpers such as assert.match() and assert.doesNotMatch().
This PR applies that same modernization to this test file.

What was changed

HTTP/1.0 test

Previously:

assert.ok(!/x-foo/.test(res_buffer));

Updated to:

assert.doesNotMatch(res_buffer, /x-foo/);

HTTP/1.1 test

Previously:

assert.ok(/0\r\nx-foo: bar\r\n\r\n$/.test(res_buffer));

Updated to:

assert.match(res_buffer, /0\r\nx-foo: bar\r\n\r\n$/);

Why this change

• Improves readability by using purpose-built assertion helpers.
• Aligns the test with modern Node.js testing conventions.
• No functional or behavioral changes to the test . Only assertion style updates.

Additional notes

• All tests continue to pass.
• No logic or behavior was altered; only assertions were updated.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/70291/

[lpinca]

• Removes reliance on RegExp.prototype.test(), which is being phased out across the codebase.

?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.54%. Comparing base (7fe8085) to head (ff496e9).
⚠️ Report is 13 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #60831   +/-   ##
=======================================
  Coverage   88.54%   88.54%           
=======================================
  Files         703      703           
  Lines      208259   208259           
  Branches    40170    40167    -3     
=======================================
+ Hits       184405   184406    +1     
- Misses      15859    15870   +11     
+ Partials     7995     7983   -12     

see 30 files with indirect coverage changes

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[cruzz77]

@lpinca Thanks for pointing that out .
I meant that many recent test modernisations replace .test() with
assert.match() / assert.doesNotMatch() for clarity.

I've removed that line to avoid implying any official deprecation.
Thank you!

[nodejs-github-bot]

Landed in 23c58f0