fix(renovate): use managerFilePatterns with proper regex syntax

renovate.json

@@ -131,8 +131,8 @@
     {
       "customType": "regex",
       "description": "Update Docker images in Jinja2 compose templates",
-      "fileMatch": [
-        "\\.j2$"
+      "managerFilePatterns": [
+        "/(^|/)library/compose/.+/compose\\.(yaml|yml)\\.j2$/"
       ],
       "matchStrings": [
         "image:\\s*(?<depName>[^:\\s]+):(?<currentValue>[^\\s\\n{]+)"