Update Pyodide workflow to use scheduled builds

Author: NikolajBjorner

.github/workflows/pyodide.yml

@@ -1,8 +1,8 @@
 name: Pyodide Build
 
 on:
-  push:
-    branches: [ master ]
+  schedule:
+    - cron: '0 0 */2 * *'
 
 env:
   BUILD_TYPE: Release