BasePlayerControl: Fix repeatMode de-sync

By removing repeatMode mirroring property we now have only single source
of truth left for this data, and we won't end up with broken bindings
after manual assignments.

Fixes possible de-sync between the state of the Repeat button and the
actual state displayed in its drop-down menu. It can be caused by
clicking on the button at least once, and then changing mode either via
button's drop-down menu or via global application menu.