Please read the documentation on this feature: Setup Remote Access Key
The only way "disable" this is by editing your WHM theme and removing the reference. The following shows how to do this:
Edit /usr/local/cpanel/whostmgr/docroot/themes/<themename>/comand Move the
ENDWHMDEFINE statement on line 331 two lines down, just after the next <br />
tag. This will cause the "Setup Remote Access Key" functionality to only
display if someone has ROOT or CLUSTERING access.
Note: you should do this in a copy of your WHM theme, otherwise the next upcp
update will overwrite your changes.
As jondalar noted, each reseller, which includes root, has a Remote Accesss Key assigned, and can create a new one, thereby invalidating the old. When a reseller creates a new Remote Access Key, it is his
key only that gets regenerated. Likewise when viewing the Remote Access key, the reseller only sees his own. Scripts and Applications that use this key for validation can only perform the same actions that the reseller could via the WHM interface.