trying to create simple plugin to filter categories from all authors

Plugins run a lot earlier than themes – you need to delay the execution using a hook:

/**
 * Fire once WordPress is ready and conditionally hook our handler.
 */
function wpse_199197_init() {
    $user = wp_get_current_user();
    $allowed_roles = array( 'author' );

    if ( array_intersect( $allowed_roles, $user->roles ) )
        add_filter( 'get_terms_args', 'wpse_77670_filterGetTermArgs', 10, 2 );
}

add_action( 'init', 'wpse_199197_init' );

function wpse_77670_filterGetTermArgs( $args, $taxonomies) {
    global $typenow;

    if ( $typenow == 'post' ) {
        // check whether we're currently filtering selected taxonomy
        if ( implode( '', $taxonomies ) == 'category' ) {
            $cats = array( 11, 13 ); // as an array

            if ( empty( $cats ) )
                $args['include'] = array( 99999999 ); // no available categories
            else
                $args['include'] = $cats;
        }
    }

    return $args;
}