Fix typo in docs using from JavaScript

* Change *not* to *now*

docs/using_pyodide_from_javascript.md

@@ -58,7 +58,7 @@ pyodide.loadPackage(['cycler', 'pytz'])
 
 ```javascript
 pyodide.loadPackage('matplotlib').then(() => {
-  // matplotlib is not available
+  // matplotlib is now available
 });
 ```