test: mark test flaky on freebsd

Test name test-worker-message-port-message-before-close is too long for
a commit message description.

Refs: https://github.com/nodejs/node/issues/31280

PR-URL: https://github.com/nodejs/node/pull/32849
Refs: https://github.com/nodejs/node/issues/28803


Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>