quic: fixup quic stream variable chunk len

[jasnell]

Fixes: #63216

[nodejs-github-bot]

Review requested:

• @nodejs/quic

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73336/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.04%. Comparing base (facd71e) to head (4ade24f).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #63230   +/-   ##
=======================================
  Coverage   90.04%   90.04%           
=======================================
  Files         713      713           
  Lines      224950   224961   +11     
  Branches    42530    42527    -3     
=======================================
+ Hits       202548   202559   +11     
+ Misses      14188    14180    -8     
- Partials     8214     8222    +8     

Files with missing lines	Coverage Δ
lib/internal/quic/quic.js	100.00% <100.00%> (ø)

... and 33 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73348/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73352/