remove dependabot due to switch to renovatebot

Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

.github/dependabot.yml

@@ -1,18 +0,0 @@
-# synced from @nextcloud/android-config
-version: 2
-updates:
-    -   package-ecosystem: "github-actions"
-        directory: "/"
-        schedule:
-            interval: "weekly"
-    -   package-ecosystem: gradle
-        directory: "/"
-        schedule:
-            interval: daily
-            time: "03:00"
-            timezone: Europe/Paris
-        rebase-strategy: "disabled"
-        open-pull-requests-limit: 10
-        labels:
-            - 3. to review
-            - dependencies