chore(deps): update sourcegraph prometheus / grafana docker images to v6.6.2517

Author: renovate[bot]

docker-compose/docker-compose.yaml

@@ -419,7 +419,7 @@ services:
   #
   prometheus:
     container_name: prometheus
-    image: 'index.docker.io/sourcegraph/prometheus:6.1.2889@sha256:75fa45933ecb03f7aca1d54ec5ebc05d11ff300494a2ca8fbaefa25c83f0326f'
+    image: 'index.docker.io/sourcegraph/prometheus:6.6.2517@sha256:554b2aee01a45878874ebc7fc92da4b0aba2bb39c826bf521ad835afe91bf097'
     cpus: 4
     mem_limit: '8g'
     volumes:
@@ -446,7 +446,7 @@ services:
   # 'GF_SERVER_ROOT_URL='https://grafana.example.com'
   grafana:
     container_name: grafana
-    image: 'index.docker.io/sourcegraph/grafana:6.3.3@sha256:2f68b9b1542e7d75459d983b606d2fdd1c11a75610464e3d7a6ced4f3ac474bf'
+    image: 'index.docker.io/sourcegraph/grafana:6.6.2517@sha256:e85a929392d51d6ebc6a76734a936ed4eab723b4d97d6ac6695b81f615c6fb88'
     cpus: 1
     mem_limit: '1g'
     volumes: