github: Disable dependabot for GHA (#420)

.github/dependabot.yml

diff --git a/.github/dependabot.yml b/.github/dependabot.yml
index 405de40..eed0ba6 100644
--- a/.github/dependabot.yml
+++ b/.github/dependabot.yml
@@ -5,9 +5,3 @@
     schedule:
       interval: "daily"
     labels: ["dependencies"]
-
-  - package-ecosystem: "github-actions"
-    directory: "/"
-    schedule:
-      interval: "daily"
-    labels: ["dependencies"]