SDK / exoplayer

The connection to a legacy MediaSession may receive additional
onSessionReady callbacks that are treated as additional state updates.
We currently also set the "notifyConnected" flag for these updates
even though we are connected already, causing an IllegalStateException.

Fix the exception by not setting this flag.

We can also remove the wording about "locked" updates since this class
operates everything on a single application thread.

Issue: androidx/media#49
PiperOrigin-RevId: 487487286
(cherry picked from commit b24161a6)