ref(aiohttp): Make DEFUALT_FAILED_REQUEST_STATUS_CODES private

[szokeasaurusrex]

There is no reason this constant should be part of the public API. Since no release has included this constant yet, making this constant private does not require a major version bump.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.30%. Comparing base (09c6f2a) to head (d64c360).
Report is 1 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3558      +/-   ##
==========================================
- Coverage   84.31%   84.30%   -0.01%     
==========================================
  Files         133      133              
  Lines       13890    13890              
  Branches     2930     2930              
==========================================
- Hits        11711    11710       -1     
  Misses       1442     1442              
- Partials      737      738       +1     

Files with missing lines	Coverage Δ
sentry_sdk/integrations/aiohttp.py	85.11% <100.00%> (ø)

... and 1 file with indirect coverage changes

[sentrivana]

Honestly this would've been fine to leave as is -- I don't see any reason for anyone to use this outside of the SDK and it's not part of the advertised API. But I'm fine either way.