Use fine-grained sponsors PR token (#4699)

This uses a fine-grained token

- **PR Description**

- **Please check if the PR fulfills these requirements**

* [ ] Cheatsheets are up-to-date (run `go generate ./...`)
* [ ] Code has been formatted (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#code-formatting))
* [ ] Tests have been added/updated (see
[here](https://github.com/jesseduffield/lazygit/blob/master/pkg/integration/README.md)
for the integration test guide)
* [ ] Text is internationalised (see
[here](https://github.com/jesseduffield/lazygit/blob/master/CONTRIBUTING.md#internationalisation))
* [ ] If a new UserConfig entry was added, make sure it can be
hot-reloaded (see
[here](https://github.com/jesseduffield/lazygit/blob/master/docs/dev/Codebase_Guide.md#using-userconfig))
* [ ] Docs have been updated if necessary
* [ ] You've read through your own file changes for silly mistakes etc

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Author: jesseduffield

.github/workflows/sponsors.yml

@@ -27,4 +27,4 @@ jobs:
           labels: "ignore-for-release"
           delete-branch: true
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_API_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.SPONSORS_PR_TOKEN }}