chore: streamline dependabot (#92)

align with
https://github.com/cap-java/cds-feature-attachments/blob/main/.github/dependabot.yml

Author: sjvans

.github/dependabot.yml

@@ -2,7 +2,7 @@ version: 2
 updates:
   - package-ecosystem: maven
     directories:
-      - "/**/*"
+      - "/"
     schedule:
       interval: daily
     open-pull-requests-limit: 10