Bluetooth: Audio: Remove ISO disconnected and connected cbs

The callbacks were implemented to notify the application
about the state of the ISO. However, since then, callbacks
such as `started` and `stopped` have been implemented,
and as such the `connected` and `disconnected` callbacks
no longer server any purpose.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>
10 files changed