ci(publish): bump actions off deprecated Node 20 runtimes (#18)

GitHub is deprecating the Node 20 action runtime; checkout@v4,
setup-python@v5, and upload/download-artifact@v4 all run on it and
were being auto-forced to Node 24 with a warning. Bump each to its
current major (checkout@v7, setup-python@v7, upload-artifact@v7,
download-artifact@v8), all of which run natively on Node 24.

.github/workflows/publish.yml

@@ -15,10 +15,10 @@ jobs:
     name: Build sdist + wheel
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v7
         with:
           fetch-depth: 0  # hatch-vcs needs full history + tags to derive the version
-      - uses: actions/setup-python@v5
+      - uses: actions/setup-python@v7
         with:
           python-version: "3.12"
       - run: python -m pip install --upgrade build
@@ -30,7 +30,7 @@ jobs:
           if ! ls dist/ | grep -q "smartthings_local-${version}"; then
             echo "Built artifacts do not match tag version ${version}"; exit 1
           fi
-      - uses: actions/upload-artifact@v4
+      - uses: actions/upload-artifact@v7
         with:
           name: dist
           path: dist/
@@ -43,7 +43,7 @@ jobs:
     permissions:
       id-token: write  # required for Trusted Publishing (OIDC)
     steps:
-      - uses: actions/download-artifact@v4
+      - uses: actions/download-artifact@v8
         with:
           name: dist
           path: dist/