docs: add note about Tempo appProtocol in proxy-trace.md

[rtomadpg]

Resolves #5887

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.83%. Comparing base (2bbbdf8) to head (1927037).
⚠️ Report is 1248 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5963      +/-   ##
==========================================
+ Coverage   65.80%   65.83%   +0.02%     
==========================================
  Files         217      217              
  Lines       36013    36013              
==========================================
+ Hits        23699    23708       +9     
+ Misses      10834    10829       -5     
+ Partials     1480     1476       -4     

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[zirain]

Thanks!

[arkodg]

instead of grpc in the key, can we use kubernetes.io/h2c instead ?
this is what upstream would ideally like
https://gateway-api.sigs.k8s.io/guides/backend-protocol/

[arkodg]

thanks @rtomadpg, added one comment, can you also copy over the same content into v1.3/tasks/observability/proxy-trace.md

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[acelinkio]

I'm coming here from using an otelcollector and not seeing really how to configure gatewayapi to send via grpc. i see commends around appProtocol.

i'll continue looking around, jsut want to mention its not readily apparent

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This pull request has been automatically marked as stale because it has not had activity in the last 30 days. Please feel free to give a status update now, ping for review, when it's ready. Thank you for your contributions!