Update prom/prometheus Docker tag to v3.8.0

Author: renovate[bot]

docker-compose.yml

@@ -140,7 +140,7 @@ services:
     restart: always
 
   prometheus:
-    image: prom/prometheus:v3.2.0@sha256:5888c188cf09e3f7eebc97369c3b2ce713e844cdbd88ccf36f5047c958aea120
+    image: prom/prometheus:v3.8.0@sha256:d936808bdea528155c0154a922cd42fd75716b8bb7ba302641350f9f3eaeba09
     command:
       - "--web.external-url=https://${PROMETHEUS_DOMAIN:-prometheus.owncloud.test}"
       - "--config.file=/etc/prometheus/prometheus.yml"