Update derived fields provisioning example (#66027)

* Update derived fields provisioning example

*WHAT*

Update loki derived fields provisioning example:
- Remove `# Right now, Grafana supports only Jaeger and Zipkin data sources as link targets.` comment since it supports other trace data sources as well such as Tempo".
- Add example to include `URL Label` to provide full configuration example that reflects the options visible on the UI.

* Update _index.md

* makes prettier

---------

Co-authored-by: lwandz13 <larissa.wandzura@grafana.com>

docs/sources/datasources/loki/_index.md

@@ -121,13 +121,14 @@ datasources:
       maxLines: 1000
       derivedFields:
         # Field with internal link pointing to data source in Grafana.
-        # Right now, Grafana supports only Jaeger and Zipkin data sources as link targets.
         # datasourceUid value can be anything, but it should be unique across all defined data source uids.
         - datasourceUid: my_jaeger_uid
           matcherRegex: "traceID=(\\w+)"
           name: TraceID
           # url will be interpreted as query for the datasource
           url: '$${__value.raw}'
+          # optional for URL Label to set a custom display label for the link.
+          urlDisplayLabel: 'View Trace'
 
         # Field with external link.
         - matcherRegex: "traceID=(\\w+)"