fix: Change Dependabot to github-actions ecosystem (no SPM)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: kochj23

.github/dependabot.yml

@@ -1,6 +1,6 @@
 version: 2
 updates:
-  - package-ecosystem: "swift"
+  - package-ecosystem: "github-actions"
     directory: "/"
     schedule:
       interval: "weekly"