Revert unusable workaround for PAUSE being sent when going NULL

Revert unusable workaround for PAUSE being sent when going NULL

Directly setting rtspsrc to the NULL state before putting the pipeline
in the NULL state usually works, but it can cause a deadlock in some
cases, so it's not a reliable mechanism to fix this.

This reverts commit f37afdafff1fd0a339966116261f5cd0de53f5d1:
"rtspsrc: Fix state changes from PAUSED to PLAYING"

and commit 76d624b2df5594a82269b94dffe8766a372d059d:
"rtspsrc: Do not send PAUSE command when going to GST_STATE_NULL"

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/908>