Update dependabot.yml

Signed-off-by: Mathieu Carbou <mathieu.carbou@gmail.com>

.github/dependabot.yml

@@ -1,20 +1,10 @@
-# To get started with Dependabot version updates, you'll need to specify which
-# package ecosystems to update and where the package manifests are located.
-# Please see the documentation for all configuration options:
-# https://docs.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+# Set update schedule for GitHub Actions
 
 version: 2
 updates:
-  - package-ecosystem: "gitsubmodule"
-    directory: "/"
-    schedule:
-      interval: "daily"
-    reviewers:
-      - "mathieucarbou"
 
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
-      interval: "daily"
-    reviewers:
-      - "mathieucarbou"
+      # Check for updates to GitHub Actions every week
+      interval: "weekly"