[PR #7651/45f98b7d backport][3.8] Fix BadStatusLine message

[patchback]

This is a backport of PR #7651 as merged into master (45f98b7).

Can't remember the issue this came up in, but the message in this exception gets escaped and doesn't display correctly.
llhttp has its own messages, so we should display them directly, rather than prefixing it with another message.

[codecov]

Codecov Report

Merging #7666 (66147ff) into 3.8 (89b7df1) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##              3.8    #7666   +/-   ##
=======================================
  Coverage   97.34%   97.34%           
=======================================
  Files         107      107           
  Lines       31122    31123    +1     
  Branches     3965     3965           
=======================================
+ Hits        30297    30298    +1     
  Misses        618      618           
  Partials      207      207           

Flag	Coverage Δ
CI-GHA	97.21% <100.00%> (+<0.01%)	⬆️
OS-Linux	96.86% <100.00%> (+<0.01%)	⬆️
OS-Windows	95.20% <100.00%> (+<0.01%)	⬆️
OS-macOS	96.61% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	94.81% <100.00%> (+<0.01%)	⬆️
Py-3.10.13	96.45% <100.00%> (+<0.01%)	⬆️
Py-3.11.0	96.12% <100.00%> (-0.05%)	⬇️
Py-3.6.15	96.32% <100.00%> (-0.01%)	⬇️
Py-3.6.8	94.72% <100.00%> (+<0.01%)	⬆️
Py-3.7.17	96.49% <100.00%> (+<0.01%)	⬆️
Py-3.7.9	94.85% <100.00%> (+<0.01%)	⬆️
Py-3.8.10	94.78% <100.00%> (+<0.01%)	⬆️
Py-3.8.18	96.39% <100.00%> (-0.06%)	⬇️
Py-3.9.13	94.78% <100.00%> (+<0.01%)	⬆️
Py-3.9.18	96.46% <100.00%> (+<0.01%)	⬆️
Py-pypy7.3.11	93.83% <100.00%> (+<0.01%)	⬆️
VM-macos-latest	96.61% <100.00%> (+<0.01%)	⬆️
VM-ubuntu-20.04	96.84% <100.00%> (-0.01%)	⬇️
VM-ubuntu-latest	96.34% <100.00%> (+<0.01%)	⬆️
VM-windows-latest	95.20% <100.00%> (+<0.01%)	⬆️

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Files	Coverage Δ
aiohttp/http_exceptions.py	100.00% <100.00%> (ø)
tests/test_http_parser.py	97.72% <100.00%> (+<0.01%)	⬆️

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