wrap lines

Author: WangTaoTheTonic

docs/running-on-yarn.md

@@ -200,7 +200,8 @@ Most of the configs are the same for Spark on YARN as for other deployment modes
   <td><code>spark.yarn.submit.waitAppCompletion</code></td>
   <td>true</td>
   <td>
-  In YARN cluster mode, controls whether the client waits to exit until the application completes. If set to true, the client process will stay alive reporting the application's status.
+  In YARN cluster mode, controls whether the client waits to exit until the application completes.
+  If set to true, the client process will stay alive reporting the application's status.
   Otherwise, the client process will exit after submission.
   </td>
 </tr>