quic: remove unused binding variable in session.cc

[jasnell]

Removing a couple stray unused variables.

@nodejs/quic

[nodejs-github-bot]

Review requested:

• @nodejs/quic

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/73238/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.03%. Comparing base (4f44c6f) to head (6e2ea36).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #63177      +/-   ##
==========================================
- Coverage   90.04%   90.03%   -0.02%     
==========================================
  Files         713      713              
  Lines      224645   224645              
  Branches    42448    42454       +6     
==========================================
- Hits       202288   202261      -27     
- Misses      14167    14176       +9     
- Partials     8190     8208      +18     

see 31 files with indirect coverage changes

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