chore(deps): update prom/prometheus docker digest to 3b9b2a1 (#14154)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

docker/docker-compose.prod.yml

@@ -94,7 +94,7 @@ services:
     container_name: immich_prometheus
     ports:
       - 9090:9090
-    image: prom/prometheus@sha256:2659f4c2ebb718e7695cb9b25ffa7d6be64db013daba13e05c875451cf51b0d3
+    image: prom/prometheus@sha256:3b9b2a15d376334da8c286d995777d3b9315aa666d2311170ada6059a517b74f
     volumes:
       - ./prometheus.yml:/etc/prometheus/prometheus.yml
       - prometheus-data:/prometheus