[CI] self-test: Reenable stereo switching conditons

In the self-test, two stereo-switching conditions are commented out and thus not tested. The disabling was done a long time ago:

Revision: afaa34db80531424795776a173703963ceb7aac8
Author: Reinhold Böhm <reinhold.boehm@dolby.com>
Date: 25-Nov-22 15:53:47
Message:
skip more high bitrate DTX tests

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Modified: scripts/config/self_test.prm
Modified: tests/test_sba_bs_enc.py

It is unclear why these tests are skipped. It is thus proposed to reenable these two stereo-switching conditions again.