Manual:$wgDisabledVariants

Language, regional and character encoding settings: $wgDisabledVariants
Disabled variants for language variant conversion.
Introduced in version:	1.16.0 (r56560)
Removed in version:	Still in use
Allowed values:	(array)
Default value:	[]
Other settings: Alphabetical | By function

Details

Disabled variants for language variant conversion.

example:

$wgDisabledVariants[] = 'zh-mo';
$wgDisabledVariants[] = 'zh-my';

or:

$wgDisabledVariants = array( 'zh-mo', 'zh-my' );