test: fix flaky permessage-deflate limit timeout

[mcollina]

Description

Fixes a flaky websocket test introduced by the maxPayloadSize: 0 coverage.

The timeout path was calling t.fail(...), which is not available on the node:test context used here, so timeouts surfaced as TypeError: t.fail is not a function instead of a normal assertion failure.

This also reduces the test payload from 100 MB to 2 MB so the "limit disabled" case still exercises a payload above the smaller limits used elsewhere in the file without depending on a slow transfer in CI.

Fixes: #5185

Validation

• ./node_modules/.bin/borp -p "test/websocket/permessage-deflate-limit.js"
• npm run lint -- --fix-dry-run test/websocket/permessage-deflate-limit.js

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.27%. Comparing base (da0eebc) to head (2432ab9).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5229   +/-   ##
=======================================
  Coverage   93.27%   93.27%           
=======================================
  Files         110      110           
  Lines       36353    36353           
=======================================
+ Hits        33907    33909    +2     
+ Misses       2446     2444    -2     

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