Bump xamarin/backport-bot-action from 1.0 to 2.0 (#386)

Bumps [xamarin/backport-bot-action](https://github.com/xamarin/backport-bot-action) from 1.0 to 2.0.
- [Commits](xamarin/backport-bot-action@v1.0...v2.0)

---
updated-dependencies:
- dependency-name: xamarin/backport-bot-action
  dependency-version: '2.0'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/backport-trigger.yml

@@ -10,7 +10,7 @@ jobs:
     if: github.event.issue.pull_request != '' && contains(github.event.comment.body, '@gitbot')
 
     steps:
-      - uses: xamarin/backport-bot-action@v1.0
+      - uses: xamarin/backport-bot-action@v2.0
         with:
           pull_request_url: ${{ github.event.issue.pull_request.url }}
           comment_body: ${{ github.event.comment.body }}