deps: remove actions updates from dependabot (#25211)

Dependabot can update actions to versions that are not in the TSCCR
allowlist. The TSCCR check doesn't happen in CE, which means we don't learn we
have a problem until after we've spent the effort to backport them. Remove the
automation that updates actions automatically until this issue is resolved on
the security team's side.

.github/dependabot.yml

@@ -40,13 +40,3 @@ updates:
     labels:
       - "theme/dependencies"
       - "theme/website"
-  - package-ecosystem: github-actions
-    open-pull-requests-limit: 5
-    directory: /
-    labels:
-      - "theme/dependencies"
-      - "theme/ci"
-    schedule:
-      interval: "weekly"
-      day: "sunday"
-      time: "09:00"