Some recurring instances are not adjusted properly

[derekantrican]

Reproducing calendar: https://pastebin.com/raw/dbNXmwZW Event UID of interest: 040000008200E00074C5B7101A82E00800000000108C9F6EC633D7010000000000000000100000002A73C0A29054164498FE95F9AC03572E (note that UIDs are broken across two lines in the ics above)

Screenshot (date shown is April 20, 20201, times in Pacific Standard Time - same as the calendar):

Basically, the April 20 instance of this recurring series was moved (from 1105 to 1435). The script seems to keep both instances, whereas Google Calendar removes the original instance.

Also noteable:

Script events:

• The first event (the old, original time) is a recurring event
• The second event (the new, correct time) is not a recurring event

Google calendar-synced events:

• The event (the new, correct time) is a recurring event

[derekantrican]

~~I believe I have tested this against the new code in #188 with the issue still present. But I can doublecheck again later~~

Edit: seems to work just fine in #188 with the exception of changing Helpers.gs line 546 to timeMin : recEvent.recurringEventId + "Z",