test: removed unused variable

Removed an unused variable in test-buffer-failed-alloc-typed-arrays.js.

PR-URL: https://github.com/nodejs/node/pull/23481


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>