doc: use await in filehandle.truncate() snippet

The example snippet of filehandle.close() uses the `await` keyword based on convention. This change updates the example snippet of filehandle.truncate() to similarly use the keyword for the purposes of consistency. PR-URL: #38939 Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Darshan Sen <[email protected]> Reviewed-By: Luigi Pinca <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Zijian Liu <[email protected]>

Author: RA80533

doc/api/fs.md

@@ -402,7 +402,7 @@ try{
  filehandle =awaitopen('temp.txt', 'r+');
 awaitfilehandle.truncate(4);
 } finally{
- filehandle?.close();
+awaitfilehandle?.close();
 }
 ```