DOC-4735 Update common '--user' option to be '--username'

Change-Id: Ie80276498e7a54febb924feebc7ecdf69a15777a
Reviewed-on: http://review.couchbase.org/c/couchbase-cli/+/146298
Well-Formed: Build Bot <build@couchbase.com>
Reviewed-by: James Lee <james.lee@couchbase.com>
Tested-by: Carlos Gonzalez <carlos.gonzalez@couchbase.com>

Author: Carlos Gonzalez Betancort

docs/generated/doc/cblogredaction/cblogredaction.html

@@ -481,7 +481,7 @@ <h2 id="_options">OPTIONS</h2>
 section for more information on specifying a hostname.</p>
 </dd>
 <dt class="hdlist1">-u</dt>
-<dt class="hdlist1">--user &lt;username&gt;</dt>
+<dt class="hdlist1">--username &lt;username&gt;</dt>
 <dd>
 <p>Specifies the username of the user executing the command. If you do not have
 a user account with permission to execute the command then it will fail with