Bump purcell/setup-emacs from 3.0 to 4.0

Bumps [purcell/setup-emacs](https://github.com/purcell/setup-emacs) from 3.0 to 4.0.
- [Release notes](https://github.com/purcell/setup-emacs/releases)
- [Commits](purcell/setup-emacs@v3.0...v4.0)

---
updated-dependencies:
- dependency-name: purcell/setup-emacs
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

Diff for: .github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: purcell/setup-emacs@v3.0
+      - uses: purcell/setup-emacs@v4.0
         with:
           version: 28.1
       - name: install dependencies