Update dependabot.yml to only one cdk directory

Author: JuliaBrigitte

.github/dependabot.yml

@@ -1,15 +1,5 @@
-version: 2
+version: 3
 updates:
-  - package-ecosystem: npm
-    directory: "/cdk"
-    schedule:
-      interval: "monthly"
-    # The version of AWS CDK libraries must match those from @guardian/cdk.
-    ignore:
-      - dependency-name: "aws-cdk"
-      - dependency-name: "aws-cdk-lib"
-      - dependency-name: "constructs"
-      
   - package-ecosystem: npm
     directory: "/cdk"
     schedule: