fix: remove obsolete jcabillot/phpapache custom manager from renovate.json

The Dockerfile already migrated to dunglas/frankenphp, the
ARG VERSION pattern is gone. The custom manager tracking
jcabillot/phpapache is no longer needed.

renovate.json

@@ -1,17 +1,3 @@
 {
-  "$schema": "https://docs.renovatebot.com/renovate-schema.json",
-  "customManagers": [
-    {
-      "customType": "regex",
-      "description": "Detect ARG VERSION pin for jcabillot/phpapache base image",
-      "managerFilePatterns": [
-        "/^Dockerfile$/"
-      ],
-      "matchStrings": [
-        "ARG\\s+VERSION=\"(?<currentValue>[^\"]+)\""
-      ],
-      "depNameTemplate": "jcabillot/phpapache",
-      "datasourceTemplate": "docker"
-    }
-  ]
+  "$schema": "https://docs.renovatebot.com/renovate-schema.json"
 }