update auto merge token

Author: lastlink

.github/workflows/dependabot_automerge.yml

@@ -11,4 +11,4 @@ jobs:
       - uses: ahmadnassri/action-dependabot-auto-merge@v2
         with:
           target: minor
-          github-token: ${{ secrets.mytoken }}
+          github-token: ${{ secrets.MYTOKEN }}