test: remove test/v8-updates/test-postmortem-metadata.js

The postmortem metadata test is no longer used to maintain
postmortem debugging tools. Since it frequently breaks on
V8 updates, it makes more sense to just remove it.

Backport-PR-URL: #34356
PR-URL: #33579
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Jiawen Geng <[email protected]>
Reviewed-By: Michael Dawson <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Shelley Vohr <[email protected]>

Author: cjihrig