In WHM you can edit any file. Login to the WHM interface. Scroll down in the menu on the left until you see the "ConfigServer Explorer" link in the "Plugins" section:
Code:
___________________________________________
| Plugins |
|___________________________________________|
| * ConfigServer Mail Manage |
| * ConfigServer Mail Queues |
| * Configure Support Request Submission |
| * Configure cPanel Cron Times |
| * ConfigServer Explorer |
|___________________________________________|
Click on the "ConfigServer Explorer" and will see all VPS folders in the main screen. Navigate in Explorer to /etc/ssh/sshd_config and fix this file.