Revert "Mark test_subport_connectivity as unstable for now"

This reverts commit c12b50cac6814bf4210b7d94fb3a1a7dc762e977.

Reason for revert: Good success rate in master and stable branches,
400+ success seen in last 14 days as per opensearch.
There was one failure in ubuntu jammy job but that's a known issue.

Change-Id: I3cc3915c9008067690af85b381db2f4acbbf47b0
Related-Bug: #1897796
Conflicts:
	neutron_tempest_plugin/scenario/test_trunk.py
1 file changed