Bump peter-evans/create-pull-request from 7 to 8 (sunpy#218)

Bumps [peter-evans/create-pull-request](https://github.com/peter-evans/create-pull-request) from 7 to 8.
- [Release notes](https://github.com/peter-evans/create-pull-request/releases)
- [Commits](peter-evans/create-pull-request@v7...v8)

---
updated-dependencies:
- dependency-name: peter-evans/create-pull-request
  dependency-version: '8'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/sub_package_update.yml

@@ -77,7 +77,7 @@ jobs:
 
       - name: Create pull request
         if: steps.cruft_json.outputs.has_changes == '1'
-        uses: peter-evans/create-pull-request@v7
+        uses: peter-evans/create-pull-request@v8
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           add-paths: "."