mention time_bucket in timescaledb tooltip

public/app/plugins/datasource/postgres/partials/config.html

@@ -42,7 +42,7 @@
 
 <div class="gf-form-group">
 	<div class="gf-form">
-		<gf-form-switch class="gf-form" label="TimescaleDB" tooltip="Use TimescaleDB features in Grafana" label-class="width-9" checked="ctrl.current.jsonData.timescaledb" switch-class="max-width-6"></gf-form-switch>
+		<gf-form-switch class="gf-form" label="TimescaleDB" tooltip="Use TimescaleDB features (e.g., time_bucket) in Grafana" label-class="width-9" checked="ctrl.current.jsonData.timescaledb" switch-class="max-width-6"></gf-form-switch>
 	</div>
 </div>