docs: Remove inaccurate LDAP coming soon notice.
docs: Remove inaccurate LDAP coming soon notice.

We implemented this feature in the series ending with the
documentation in 2abe3251478ca42c2b3c3df5f0e26d066191a874.

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