Update prepare-patch-release.yml

Author: lzchen

.github/workflows/prepare-patch-release.yml

@@ -19,6 +19,9 @@ jobs:
             exit 1
           fi
 
+      - name: Install toml
+        run: pip install toml
+
       - name: Set environment variables
         run: |
           stable_version=$(./scripts/eachdist.py version --mode stable)