Update manage-caches.md to use ${{ github.token }} in the example

This is better than implying/asking the user to create a secret called GITHUB_TOKEN, which is kinda the legacy way of giving Actions the ability to call back to Github APIs.

Author: DrEsteban

content/actions/how-tos/managing-workflow-runs-and-deployments/managing-workflow-runs/manage-caches.md

@@ -76,7 +76,7 @@ jobs:
           done
           echo "Done"
         env:
-          GH_TOKEN: {% raw %}${{ secrets.GITHUB_TOKEN }}{% endraw %}
+          GH_TOKEN: {% raw %}${{ github.token }}{% endraw %}
           GH_REPO: {% raw %}${{ github.repository }}{% endraw %}
           BRANCH: refs/pull/{% raw %}${{ github.event.pull_request.number }}{% endraw %}/merge
 ```