Fix incorrect websocket upgrade

[Dreamsorcerer]

Just rely on the parser, instead of attempting to reparse.

[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.95%. Comparing base (5a9777d) to head (616c370).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
tests/test_web_websocket_functional.py	81.81%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master   #12723       +/-   ##
===========================================
+ Coverage   47.33%   98.95%   +51.61%     
===========================================
  Files         131      131               
  Lines       46732    46744       +12     
  Branches     2420     2420               
===========================================
+ Hits        22120    46254    +24134     
+ Misses      24006      368    -23638     
+ Partials      606      122      -484     

Flag	Coverage Δ
Autobahn	22.43% <7.69%> (-0.01%)	⬇️
CI-GHA	98.92% <84.61%> (?)
OS-Linux	98.67% <84.61%> (?)
OS-Windows	97.04% <84.61%> (?)
OS-macOS	97.93% <84.61%> (?)
Py-3.10	98.15% <84.61%> (?)
Py-3.11	98.41% <84.61%> (?)
Py-3.12	98.50% <84.61%> (?)
Py-3.13	98.47% <84.61%> (?)
Py-3.14	98.49% <84.61%> (?)
Py-3.14t	97.55% <84.61%> (?)
Py-pypy-3.11	97.42% <84.61%> (?)
VM-macos	97.93% <84.61%> (?)
VM-ubuntu	98.67% <84.61%> (?)
VM-windows	97.04% <84.61%> (?)
cython-coverage	37.95% <7.69%> (-0.01%)	⬇️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 72 untouched benchmarks
⏩ 72 skipped benchmarks¹

---

_{Comparing fix-upgrade (616c370) with master (5a9777d)}

Footnotes

1. 72 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. ↩

[patchback]

Backport to 3.14: 💔 cherry-picking failed — conflicts found

❌ Failed to cleanly apply 2a4247b on top of patchback/backports/3.14/2a4247b1adba3c9a6b1cb0bd6135f332f8ff2f3a/pr-12723

Backporting merged PR #12723 into master

1. Ensure you have a local repo clone of your fork. Unless you cloned it
   from the upstream, this would be your origin remote.
2. Make sure you have an upstream repo added as a remote too. In these
   instructions you'll refer to it by the name upstream. If you don't
   have it, here's how you can add it:

   $ git remote add upstream https://github.com/aio-libs/aiohttp.git

3. Ensure you have the latest copy of upstream and prepare a branch
   that will hold the backported code:

   $ git fetch upstream
   $ git checkout -b patchback/backports/3.14/2a4247b1adba3c9a6b1cb0bd6135f332f8ff2f3a/pr-12723 upstream/3.14

4. Now, cherry-pick PR Fix incorrect websocket upgrade #12723 contents into that branch:

   $ git cherry-pick -x 2a4247b1adba3c9a6b1cb0bd6135f332f8ff2f3a

   If it'll yell at you with something like fatal: Commit 2a4247b1adba3c9a6b1cb0bd6135f332f8ff2f3a is a merge but no -m option was given., add -m 1 as follows instead:

   $ git cherry-pick -m1 -x 2a4247b1adba3c9a6b1cb0bd6135f332f8ff2f3a

5. At this point, you'll probably encounter some merge conflicts. You must
   resolve them in to preserve the patch from PR Fix incorrect websocket upgrade #12723 as close to the
   original as possible.
6. Push this branch to your fork on GitHub:

   $ git push origin patchback/backports/3.14/2a4247b1adba3c9a6b1cb0bd6135f332f8ff2f3a/pr-12723

7. Create a PR, ensure that the CI is green. If it's not — update it so that
   the tests and any other checks pass. This is it!
   Now relax and wait for the maintainers to process your pull request
   when they have some cycles to do reviews. Don't worry — they'll tell you if
   any improvements are necessary when the time comes!

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