docs: use relative links for Grafana dashboards

Ensure the linked file matches the current blocky version, not what's
in main, which is no longer the same since switch to single branch dev.

docs/prometheus_grafana.md

@@ -25,7 +25,7 @@ Following metrics will be exported:
 ### Grafana dashboard
 
 Example [Grafana](https://grafana.com/) dashboard
-definition [as JSON](https://github.com/0xERR0R/blocky/blob/main/docs/blocky-grafana.json)
+definition [as JSON](blocky-grafana.json)
 or [at grafana.com](https://grafana.com/grafana/dashboards/13768)
 ![grafana-dashboard](grafana-dashboard.png).
 
@@ -45,7 +45,7 @@ blocky, prometheus (with configured scraper for blocky) and grafana with prometh
 ## MySQL / MariaDB
 
 If database query logging is activated (see [Query logging](configuration.md#query-logging)), you can use following
-Grafana Dashboard [as JSON](https://github.com/0xERR0R/blocky/blob/main/docs/blocky-query-grafana.json)
+Grafana Dashboard [as JSON](blocky-query-grafana.json)
 or [at grafana.com](https://grafana.com/grafana/dashboards/14980)
 
 ![grafana-dashboard](grafana-query-dashboard.png).
@@ -54,6 +54,6 @@ Please define the MySQL source in Grafana, which points to the database with blo
 
 ## Postgres
 
-The JSON for a Grafana dashboard equivalent to the MySQL/MariaDB version is located [here](https://github.com/0xERR0R/blocky/blob/main/docs/blocky-query-grafana-postgres.json)
+The JSON for a Grafana dashboard equivalent to the MySQL/MariaDB version is located [here](blocky-query-grafana-postgres.json)
 
 --8<-- "docs/includes/abbreviations.md"