Bump actions/download-artifact from 4 to 7 (p4lang#5466)

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Author: dependabot[bot]

.github/workflows/docs-deploy.yml

@@ -20,7 +20,7 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Download Artifact from Build
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v7
         with:
           name: doxygen-html
           path: build-results