Group gardener dependencies in dependabot configuration (#1758)

* Group gardener dependencies in dependabot configuration

* Align indents

Author: hebelsan

.github/dependabot.yml

@@ -18,6 +18,11 @@ updates:
       applies-to: "version-updates"
       patterns:
       - "github.com/aws/*"
+    gardener-dependencies:
+      applies-to: "version-updates"
+      patterns:
+      - "github.com/gardener/gardener"
+      - "github.com/gardener/gardener/*"
   ignore:
   - dependency-name: "k8s.io/*"
   - dependency-name: "sigs.k8s.io/*"