otelhttp: Ignore informational response status codes when persisting status

[VirrageS]

Closes #6912

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.6%. Comparing base (3ea6585) to head (5e505fb).
Report is 5 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #6913   +/-   ##
=====================================
  Coverage   75.5%   75.6%           
=====================================
  Files        207     207           
  Lines      19319   19364   +45     
=====================================
+ Hits       14601   14653   +52     
+ Misses      4283    4275    -8     
- Partials     435     436    +1     

Files with missing lines	Coverage Δ
...ux/otelmux/internal/request/resp_writer_wrapper.go	100.0% <100.0%> (ø)
...p/otelhttp/internal/request/resp_writer_wrapper.go	100.0% <100.0%> (ø)

... and 6 files with indirect coverage changes

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[VirrageS]

@dmathieu Should I add it to Changelog?

[dmathieu]

Yes, please