Make SVG size argument optional (#12814)

Now defaults to 16 on both frontend and backend.

Co-authored-by: techknowlogick <techknowlogick@gitea.io>

templates/admin/org/list.tmpl

@@ -38,7 +38,7 @@
 							<td>
 								<a href="{{.HomeLink}}">{{.Name}}</a>
 								{{if .Visibility.IsPrivate}}
-									<span class="text gold">{{svg "octicon-lock" 16}}</span>
+									<span class="text gold">{{svg "octicon-lock"}}</span>
 								{{end}}
 							</td>
 							<td>{{.NumTeams}}</td>