fix: hydra prometheus link in docs (#1706)

fix prometheus link in docs

Author: josxha

docs/self-hosted/operations/15_observability.md

@@ -9,6 +9,6 @@ All Ory services expose an endpoint for snapshots of data collected by Prometheu
 for all projects. If you run the default configuration, it will be exposed at:
 
 - Ory Kratos: `http://{host}:4434/metrics/prometheus`
-- Ory Hydra: `http://{host}:4445/metrics/prometheus`
+- Ory Hydra: `http://{host}:4445/admin/metrics/prometheus`
 - Ory Keto: `http://{host}:4468/metrics/prometheus`
 - Ory Oathkeeper `http://{host}:9000/metrics/prometheus`