chore(deps): update mysql docker tag to v9

Author: renovate[bot]

opentofu/modules/vultr/instance/userdata/ghost-compose/compose.yml.tftpl

@@ -74,7 +74,7 @@ services:
       - ghost_network
 
   db:
-    image: mysql:8.4.8@sha256:be18eb9dc45eea9b86cb74f8c68ab92ce8569ecc37ea4e6fade02e37036c5ff4
+    image: mysql:9.6.0@sha256:c1667ed4366709204bdf4514c7d979dfdbc29af43f9840def436b039eefc5f88
     restart: always
     expose:
       - "3306"