integration: Update Zendesk Documentation.
integration: Update Zendesk Documentation.

I have updated the docs for the Zendesk to integration to include
numbers to make it easily readable.

Fixes part of #17633.

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