[PR #7651/45f98b7d backport][3.9] 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 #7667 (9a3827d) into 3.9 (b282ff9) will increase coverage by 0.22%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##              3.9    #7667      +/-   ##
==========================================
+ Coverage   97.08%   97.31%   +0.22%     
==========================================
  Files         107      107              
  Lines       31816    31822       +6     
  Branches     3005     3714     +709     
==========================================
+ Hits        30888    30967      +79     
+ Misses        708      651      -57     
+ Partials      220      204      -16     

Flag	Coverage Δ
CI-GHA	97.22% <100.00%> (+0.19%)	⬆️
OS-Linux	96.91% <100.00%> (+0.71%)	⬆️
OS-Windows	94.42% <100.00%> (+<0.01%)	⬆️
OS-macOS	96.56% <100.00%> (?)
Py-3.10.11	94.33% <100.00%> (+<0.01%)	⬆️
Py-3.10.13	96.75% <100.00%> (?)
Py-3.11.5	96.44% <100.00%> (?)
Py-3.8.10	94.31% <100.00%> (+<0.01%)	⬆️
Py-3.8.18	96.68% <100.00%> (?)
Py-3.9.13	94.31% <100.00%> (+<0.01%)	⬆️
Py-3.9.18	96.72% <100.00%> (?)
Py-pypy7.3.11	96.20% <100.00%> (+<0.01%)	⬆️
VM-macos	96.56% <100.00%> (?)
VM-ubuntu	96.91% <100.00%> (+0.71%)	⬆️
VM-windows	94.42% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
aiohttp/http_exceptions.py	100.00% <100.00%> (ø)
tests/test_http_parser.py	99.17% <100.00%> (+<0.01%)	⬆️

... and 16 files with indirect coverage changes

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