Update prom/prometheus Docker tag to v3.4.0

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:v3.4.0@sha256:78ed1f9050eb9eaf766af6e580230b1c4965728650e332cd1ee918c0c4699775
     command:
       - "--web.external-url=https://${PROMETHEUS_DOMAIN:-prometheus.owncloud.test}"
       - "--config.file=/etc/prometheus/prometheus.yml"