clock: continue to convert when paused

The paused state is already sent to all outputs, outputs might want to convert timestamps while paused.

This is the case for the SPU output that need to select subptictures to be displayed while paused. The SPU output still won't select the next subptictures, since the vout will be paused and will always try to play the same picture with the same converted TS.

Fixes #28429 (closed)