Update postgres Docker tag to v15

Author: renovate[bot]

docker-compose.test.yml

@@ -17,7 +17,7 @@ services:
     - ./scripts:/etc/netbox/scripts:z,ro
     - netbox-media-files:/opt/netbox/netbox/media:z
   postgres:
-    image: postgres:14-alpine
+    image: postgres:15-alpine
     env_file: env/postgres.env
   redis:
     image: redis:7-alpine

docker-compose.yml

@@ -33,7 +33,7 @@ services:
 
   # postgres
   postgres:
-    image: postgres:14-alpine
+    image: postgres:15-alpine
     env_file: env/postgres.env
     volumes:
     - netbox-postgres-data:/var/lib/postgresql/data