Fixing elasticsearch auth username help text's title

Bug1217126
Signed-off-by: Aaron Wells <aaronw@catalyst.net.nz>
Change-Id: I084d88eb9c638e52a12b2dea634ba94f07c3c824

htdocs/search/elasticsearch/lang/en.utf8/help/forms/pluginconfig.username.html

-<h3>Auth password</h3>
+<h3>Auth username</h3>
 
 <p>If your elasticsearch server requires an HTTP basic auth username and password to access
 it, you may provide the <strong>username</strong> here. (The core elasticsearch software