Remove the deprecated otelhttp Client

[MrAlias]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.3%. Comparing base (e5b89b0) to head (9928aed).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #8266   +/-   ##
=====================================
  Coverage   82.3%   82.3%           
=====================================
  Files        194     193    -1     
  Lines      13798   13780   -18     
=====================================
- Hits       11357   11345   -12     
+ Misses      2033    2030    -3     
+ Partials     408     405    -3     

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[Copilot]

Pull request overview

This PR removes the deprecated DefaultClient, Get, Head, Post, and PostForm convenience functions from the otelhttp package. These functions were previously marked as deprecated, and users are now expected to create their own *http.Client using otelhttp.NewTransport(http.DefaultTransport) for HTTP client instrumentation.

• Complete removal of deprecated client convenience wrapper functions
• Removal of associated test coverage for the deprecated functions
• CHANGELOG entry documenting the breaking change

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
instrumentation/net/http/otelhttp/client.go	Removes the entire file containing DefaultClient variable and Get, Head, Post, and PostForm convenience functions
instrumentation/net/http/otelhttp/client_test.go	Removes all tests for the deprecated client convenience functions
CHANGELOG.md	Adds entry in the "Removed" section documenting the breaking change with migration guidance

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