Remove 'Failed to retrieve and generate the Access Token' in the log

[Valentina R]

From 4.1.4 this line gets written for every single user (customers, staff members without the connected gCal). Can we NOT add this line for those that do not have the gCal connection set up? It's just messing up the log file and confusing users.

Reported here: https://bookingwp.com/forums/topic/strange-entries-appearing-in-gcal-log-since-the-4-1-4-update/

[Željan Topić]

Fixed with 4.1.5. Removed unnecessary logging for each access token generation.