Bump the actions group with 6 updates (#1910)

- Updates `actions/checkout` from 4 to 6
- Updates `docker/login-action` from 3 to 4
- Updates `Chizkiyahu/delete-untagged-ghcr-action` from 5 to 6
- Updates `actions/upload-artifact` from 4 to 7
- Updates `actions/download-artifact` from 4 to 8
- Updates `cygwin/cygwin-install-action` from 4 to 6

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

.github/workflows/create-release-docs.yml

@@ -10,11 +10,11 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout rgbds@release
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           path: rgbds
       - name: Checkout rgbds-www@master
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           repository: ${{ github.repository_owner }}/rgbds-www
           path: rgbds-www