deactivate failing OSBA ltv cases to not block merges

• Requested reviewers: @pihlajakuja

The newest addition to self_test_ltv.prm (2 OSBA cases with PLC), seem to trigger bit errors, see here: https://forge.3gpp.org/rep/ivas-codec-pc/ivas-codec/-/jobs/192635. This was not detected as the associated MR was merged without running the long selftest. The underlying issue may be related to #908 (closed), so I first commented there and did not file a new issue yet.