settings.html: Fixup filename for custom.ini (#6463)

public/app/features/admin/partials/settings.html

@@ -7,7 +7,7 @@
 	</div>
 
 		<div class="grafana-info-box span8" style="margin: 20px 0 25px 0">
-			These system settings are defined in grafana.ini or grafana.custom.ini (or overriden in ENV variables).
+			These system settings are defined in grafana.ini or custom.ini (or overriden in ENV variables).
 			To change these you currently need to restart grafana.
 		</div>