Delete rebase.yml

PRs from forks are not supported at the moment.

.github/workflows/rebase.yml

@@ -1,17 +0,0 @@
-on: 
-  issue_comment:
-    types: [created]
-name: Automatic Rebase
-jobs:
-  rebase:
-    name: Rebase
-    if: github.event.issue.pull_request != '' && contains(github.event.comment.body, '/rebase')
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@master
-      with:
-        fetch-depth: 0
-    - name: Automatic Rebase
-      uses: cirrus-actions/rebase@1.2
-      env:
-        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}