Update uselagoon/valkey-8 Docker tag to v26.4.0 (#2469)

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

Author: renovate[bot]

docker-compose.yml

@@ -214,7 +214,7 @@ services:
 
   #;< SERVICE_REDIS
   redis:
-    image: uselagoon/valkey-8:26.3.0
+    image: uselagoon/valkey-8:26.4.0
     #;< HOSTING_LAGOON
     labels:
       lagoon.type: redis # Change to 'none' if dedicated Redis service is used. See https://docs.lagoon.sh/using-lagoon-advanced/service-types/