http2: remove redundant request stream binding

[trivikr]

This relates to...

Redundant HTTP/2 request-stream binding in client-h2.js.

Rationale

The normal HTTP/2 request path was calling bindRequestToStream() twice for the same stream. The first call used null cleanup and was immediately replaced by the second binding with releaseRequestStream, so it was redundant.

Changes

• Remove the redundant initial bindRequestToStream(request, stream, null) call from the HTTP/2 request path.
• Add regression coverage for abort-before-response handling after an HTTP/2 stream has been assigned, ensuring request stream references are cleared.

Features

N/A

Bug Fixes

N/A

Breaking Changes and Deprecations

N/A

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Benchmarked (optional)
• Documented
• Review ready
• In review
• Merge ready

Assisted-by: openai:gpt-5.5

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.23%. Comparing base (314ba6a) to head (6e568f7).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5302   +/-   ##
=======================================
  Coverage   93.23%   93.23%           
=======================================
  Files         110      110           
  Lines       36575    36574    -1     
=======================================
+ Hits        34099    34101    +2     
+ Misses       2476     2473    -3     

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