How to restrict allowed file types for user uploads?

Hello,

I am trying to restrict which file types can be uploaded by non-admin users. I have the following code in a mu-plugin, but it seemingly has no effect on which file types can be uploaded by users on their frontend WPUM account page (for example, I can still upload ‘.docx’ files):

add_filter('upload_mimes','jr_restrict_allowed_file_types');

/**
 * Define a custom list of allowed file types for user uploads. Exclude admins.
 *
 * @param array $mime_types Array of allowed file types.
 * @return array The (modified) array of file types.
 */
function jr_restrict_allowed_file_types($mime_types) {

    if (!current_user_can('administrator')) {
        $mime_types = array(
            'jpg|jpeg|jpe' => 'image/jpeg',
            'png' => 'image/png',
            'gif' => 'image/gif',
        );
    }

    return $mime_types;
}

Is there any way to restrict which file types can be uploaded on the WPUM user account page?

Thanks. ??

/jenny