help: Fix invite-new-users.md to show all options of 'who can invite'.
help: Fix invite-new-users.md to show all options of 'who can invite'.

This commit fixes invite-new-users.md to show all the options of who
can invite under "Are invitations required for joining the organization?"
and makes this page similar to help pages for other policies.

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