backport-action: update workflow

- set permissions explicitly, as recommended in their docs
- drop github_token and github_workspace (now set per default)
- ownership has moved from "zeebe-io" to the main developer "korthout"

backport-action will follow semver from now on

.github/workflows/backport.yml

@@ -2,6 +2,9 @@ name: Backport
 on:
   pull_request_target:
     types: [closed, labeled]
+permissions:
+  contents: write # so it can comment
+  pull-requests: write # so it can create pull requests
 jobs:
   backport:
     name: Backport Pull Request
@@ -10,10 +13,8 @@ jobs:
     steps:
       - uses: actions/checkout@v3
       - name: Create backport PRs
-        uses: zeebe-io/backport-action@v1.0.1
+        uses: korthout/backport-action@v1.0.1
         with:
-          # Config README: https://github.com/zeebe-io/backport-action#backport-action
-          github_token: ${{ secrets.GITHUB_TOKEN }}
-          github_workspace: ${{ github.workspace }}
+          # Config README: https://github.com/korthout/backport-action#backport-action
           pull_description: |-
             Automatic backport to `${target_branch}`, triggered by a label in #${pull_number}.