integrations: Update Google Calendar Docs.
integrations: Update Google Calendar Docs.

I have updated the docs for the Google Celndar integration to include
numbers to increase its readbility.

Fixes part of #17633.

hackerkid/zulip,punchagan/zulip,rht/zulip,hackerkid/zulip,hackerkid/zulip,eeshangarg/zulip,rht/zulip,eeshangarg/zulip,kou/zulip,punchagan/zulip,punchagan/zulip,andersk/zulip,andersk/zulip,kou/zulip,zulip/zulip,zulip/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,kou/zulip,andersk/zulip,hackerkid/zulip,punchagan/zulip,andersk/zulip,hackerkid/zulip,kou/zulip,kou/zulip,andersk/zulip,punchagan/zulip,kou/zulip,zulip/zulip,hackerkid/zulip,eeshangarg/zulip,hackerkid/zulip,zulip/zulip,rht/zulip,rht/zulip,zulip/zulip,punchagan/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,rht/zulip,zulip/zulip,punchagan/zulip,kou/zulip,eeshangarg/zulip,andersk/zulip,eeshangarg/zulip