Update permissions and events for workflow

This commit makes a few notable changes:

1. Use the GitHub Actions automatic token for committing changes
2. Include workflow file in paths to trigger workflow
3. Checkout the default branch explicitly

Author: andyfeller

.github/workflows/third-party-licenses.yml

@@ -4,10 +4,11 @@ on:
     branches:
       - trunk
     paths:
+      - .github/licenses.tmpl
+      - .github/workflows/third-party-licenses.yml
       - go.mod
       - go.sum
-      - ".github/licenses.tmpl"
-      - "script/licenses*"
+      - script/licenses*
 jobs:
   # This job is responsible for updating the third-party license reports and source code.
   # It should be safe to cancel as the latest version of `go.mod` should be checked in.
@@ -16,11 +17,13 @@ jobs:
     concurrency:
       group: ${{ github.workflow }}
       cancel-in-progress: true
+    permissions:
+      contents: write
     steps:
       - name: Check out code
         uses: actions/checkout@v4
         with:
-          token: ${{ secrets.AUTOMATION_TOKEN }}
+          ref: trunk
 
       - name: Set up Go
         uses: actions/setup-go@v5