Customizing WooCommerce Core Checkout Fields (Removing Address Line 2) and also change the placeholder text of Address Line 1

customize-woocommerce-checkout-fields.php

<?php
/**
 * Remove Address Line 2 from WooCommerce Billing & Shipping Form
 * Also add proper placeholder for Address line 1 to include the full address
 * @author Acnam Infotech
 */
add_filter( 'woocommerce_checkout_fields', function( $fields ) {
	if( is_array( $fields ) ) {
		// Remove Address Line 2 from Billing & Shipping fields
		unset( $fields['billing']['billing_address_2'] );
		unset( $fields['shipping']['shipping_address_2'] );

		// Change the placeholder for Address Line 1 for Billing & Shipping address section
		$fields['billing']['billing_address_1']['placeholder'] = 'House no, street, apartment, suite, unit';
		$fields['shipping']['shipping_address_1']['placeholder'] = 'House no, street, apartment, suite, unit';
	}

	return $fields;
} );

/**
 * Updating the default WooCommerce Country Local values for changing placeholder texts properly
 */
add_filter('woocommerce_get_country_locale_default', function( $default_locales ) {
	if( is_array( $default_locales ) ) {
		foreach( $default_locales as $key => $value ) {
			if( $key === 'address_1' ) {
				$default_locales['address_1']['placeholder'] = 'House no, street, apartment, suite, unit';
			}
		}
	}
	return $default_locales;
});