help center: Small update to Okta SAML set up instructions.
help center: Small update to Okta SAML set up instructions.

The UI seems slightly different than before, making the metadata harder
to find - this additional description of how to get to it should be
helpful.

andersk/zulip,rht/zulip,rht/zulip,zulip/zulip,andersk/zulip,andersk/zulip,rht/zulip,zulip/zulip,andersk/zulip,andersk/zulip,andersk/zulip,zulip/zulip,zulip/zulip,rht/zulip,zulip/zulip,andersk/zulip,zulip/zulip,rht/zulip,rht/zulip,zulip/zulip,rht/zulip