Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/deploy-pypi.yml

@@ -28,7 +28,7 @@ jobs:
     name: Build distribution
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install libegl1
         run: |
           sudo apt update && sudo apt install -y libegl1
@@ -106,7 +106,7 @@ jobs:
       # PySide6 has Windows ARM64 build since 6.9.0
       PYSIDE6_LATEST_VERSION: "6.9.1"
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Install macOS dependencies
         run: |
           brew install create-dmg