Bump peter-evans/create-pull-request from 5 to 6

Bumps [peter-evans/create-pull-request](https://github.com/peter-evans/create-pull-request) from 5 to 6.
- [Release notes](https://github.com/peter-evans/create-pull-request/releases)
- [Commits](https://github.com/peter-evans/create-pull-request/compare/v5...v6)

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

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/update_backend.yml

@@ -53,7 +53,7 @@ jobs:
           sed -i "s/^__symbolic_regression_jl_version__ = .*/__symbolic_regression_jl_version__ = \"${{ steps.get-latest.outputs.version }}\"/" pysr/version.py
 
       - name: "Create PR"
-        uses: peter-evans/create-pull-request@v5
+        uses: peter-evans/create-pull-request@v6
         with:
           token: ${{ secrets.REPO_SCOPED_TOKEN }}
           title: "Automated update to backend: v${{ steps.get-latest.outputs.version }}"