fix(mail): remove unused directive in mail editor

UI/Templates/MailerUI/UIxMailEditor.wox

@@ -62,7 +62,6 @@
           </md-autocomplete>
           <md-button class="sg-icon-button"
                      ng-click="editor.send()"
-                     ng-hide="editor.saveAsTemplate"
                      ng-disabled="!(editor.message.editable.to.length > 0 || editor.message.editable.cc.length > 0 || editor.message.editable.bcc.length > 0) || editor.uploader.isUploading || messageForm.$invalid || messageForm.$submitted"
                      sg-ripple-click="mailEditor">
             <md-icon>send</md-icon>