Remove state field from woocommerce checkout form.

plugin.php

<?php
/**
 * Remove state field from woocommerce checkout form.
 *
 * @see https://github.com/woocommerce/woocommerce/blob/3.1.2/includes/class-wc-countries.php#L629
 *
 * @param array $fields Array of default address fields.
 */
function jeherve_remove_state_field( $fields ) {
	unset( $fields['state'] );

	return $fields;
}
add_filter( 'woocommerce_default_address_fields', 'jeherve_remove_state_field' );