fix: wrong example in readme

Author: janb87

README.md

@@ -42,7 +42,7 @@ steps:
   - name: Run SettleMint CLI
     uses: settlemint/settlemint-action@main
     with:
-      command: "workspace list"
+      command: "platform list workspaces"
       access-token: ${{ secrets.SETTLEMINT_ACCESS_TOKEN }}
 ```