Remove gCal rules when disconnecting the gCal

[Valentina R]

When one disconnects the gCal, the synced events from gCal are still being calculated for availability, but not shown in the backend, so customers don’t understand what’s happening.

The rules need to be removed or not taken into account when calculating the available slots.

Reported here.

[Željan Topić]

Also remove synced events from Google calendar that is different from the one that was synced.

[Valentina R]

Duplicate of #620.