Remove the deprecated WithRouteTag option in otelhttp

[MrAlias]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.3%. Comparing base (a0bd0ef) to head (02552d8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #8268     +/-   ##
=======================================
- Coverage   82.3%   82.3%   -0.1%     
=======================================
  Files        193     193             
  Lines      13778   13769      -9     
=======================================
- Hits       11343   11334      -9     
  Misses      2030    2030             
  Partials     405     405             

Files with missing lines	Coverage Δ
instrumentation/net/http/otelhttp/handler.go	92.1% <ø> (-0.6%)	⬇️

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[Copilot]

Pull request overview

This PR removes the deprecated WithRouteTag function from the otelhttp instrumentation package. The function was previously deprecated because HTTP routes are now automatically added to spans, and for metrics, users should use WithMetricAttributesFn instead.

• Removed the WithRouteTag function from handler.go
• Removed the associated test TestWithRouteTag from handler_test.go and cleaned up the unused semconv import
• Updated CHANGELOG.md to document the removal in the "Removed" section

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
instrumentation/net/http/otelhttp/handler.go	Removed the deprecated WithRouteTag function (22 lines)
instrumentation/net/http/otelhttp/handler_test.go	Removed the TestWithRouteTag test and cleaned up the unused semconv import
CHANGELOG.md	Added changelog entry documenting the removal, though contains an extraneous line about WithPublicEndpointFn

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