Revert "basesink: Take PREROLL_LOCK in wait_event()"
Revert "basesink: Take PREROLL_LOCK in wait_event()"

This reverts commit 828a4627db0cb6a6706b96d9be97e5e5c7d22215.

The lock was already taken elsewhere, in gst_base_sink_event().

StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer,StreamUtils/gstreamer