chore: switch dependabot to check for github actions (#236)

We don't check in lock files, so we don't need to check for Dart dependencies

Co-authored-by: Ademola Fadumo <48495111+demolaf@users.noreply.github.com>

Author: kevmoo

.github/dependabot.yaml

@@ -1,7 +1,6 @@
 version: 2
-enable-beta-ecosystems: true
 updates:
-  - package-ecosystem: "pub"
+  - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
-      interval: "weekly"
+      interval: "monthly"