Change dashboards collection name to be qdrant compatible

Qdrant doesn't allow ':' in collection names, so replace them with
'.'. In future we might want to follow their [recommendations]
and only using one collection but this will work for now.

[recommendations]: https://qdrant.tech/documentation/faq/qdrant-fundamentals/#how-many-collections-can-i-create

provisioning/plugins/grafana-llm-app.yaml

@@ -13,7 +13,7 @@ apps:
         qdrant:
           address: qdrant:6334
         collections:
-          - name: grafana:core:dashboards
+          - name: grafana.core.dashboards
             model: text-embedding-ada-002
             dimension: 1536