upgrade docker postgres dev version to postgres15

Part-of: <https://dev.funkwhale.audio/funkwhale/funkwhale/-/merge_requests/2771>

.env.dev

@@ -18,6 +18,6 @@ MEDIA_ROOT=/data/media
 # FORCE_HTTPS_URLS=True
 
 # Customize to your needs
-POSTGRES_VERSION=11
+POSTGRES_VERSION=15
 DEBUG=true
 TYPESENSE_API_KEY="apikey"

dev.yml

@@ -25,7 +25,7 @@ services:
     env_file:
       - .env.dev
       - .env
-    image: postgres:${POSTGRES_VERSION-11}-alpine
+    image: postgres:${POSTGRES_VERSION-15}-alpine
     environment:
       - "POSTGRES_HOST_AUTH_METHOD=trust"
     command: postgres ${POSTGRES_ARGS-}