test: unmark test-gc-http-client-onerror flaky

The test has not failed on FreeBSD in the last 100 runs and appears to
perhaps not be an issue anymore.

Closes: #23089
test-gc-http-client-onerror: PASS,FLAKY

PR-URL: #28429
Fixes: #23089
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

test/parallel/parallel.status

@@ -33,7 +33,5 @@ test-async-hooks-http-parser-destroy: PASS,FLAKY
 [$system==solaris] # Also applies to SmartOS
 
 [$system==freebsd]
-# https://github.com/nodejs/node/issues/23089
-test-gc-http-client-onerror: PASS,FLAKY
 
 [$system==aix]