ci: fix path separator

Author: Soham Dasgupta

.github/workflows/release.yml

@@ -20,7 +20,7 @@ jobs:
       - name: Build Polygon
         shell: pwsh
         if: startsWith(github.ref, 'refs/tags/v')
-        run: $GITHUB_WORKSPACE/polygon.ps1;
+        run: $GITHUB_WORKSPACE\polygon.ps1;
       - name: Upload to GitHub release
         uses: softprops/action-gh-release@v1
         if: startsWith(github.ref, 'refs/tags/v')