simplify quickstart

only give one possible ssh url syntax, all others are documented in usage chapter.

docs/quickstart.rst

@@ -247,9 +247,7 @@ is installed on the remote host, in which case the following syntax is used::
 
   $ borg init user@hostname:/path/to/repo
 
-or::
-
-  $ borg init ssh://user@hostname:port/path/to/repo
+Note: please see the usage chapter for a full documentation of repo URLs.
 
 Remote operations over SSH can be automated with SSH keys. You can restrict the
 use of the SSH keypair by prepending a forced command to the SSH public key in