Bump actions/upload-pages-artifact from 3 to 4 (#43)

Author: dependabot[bot]

.github/workflows/docs.yml

@@ -26,7 +26,7 @@ jobs:
     - name: Build
       run: zig build docs
     - name: Upload
-      uses: actions/upload-pages-artifact@v3
+      uses: actions/upload-pages-artifact@v4
       with:
         path: "zig-out/docs/"