add nonce field to review notice

Author: dannyvankooten

includes/admin/class-review-notice.php

@@ -69,7 +69,7 @@ public function show() {
 		echo esc_html__( 'You\'ve been using Mailchimp for WordPress for some time now; we hope you love it!', 'mailchimp-for-wp' ), ' <br />';
 		echo sprintf( wp_kses( __( 'If you do, please <a href="%s">leave us a 5★ rating on WordPress.org</a>. It would be of great help to us.', 'mailchimp-for-wp' ), array( 'a' => array( 'href' => array() ) ) ), 'https://wordpress.org/support/view/plugin-reviews/mailchimp-for-wp?rate=5#new-post' );
 		echo '</p>';
-		echo '<form method="POST" id="mc4wp-dismiss-review-form"><button type="submit" class="notice-dismiss"><span class="screen-reader-text">', esc_html__( 'Dismiss this notice.', 'mailchimp-for-wp' ), '</span></button><input type="hidden" name="_mc4wp_action" value="dismiss_review_notice"/></form>';
+		echo '<form method="POST" id="mc4wp-dismiss-review-form"><button type="submit" class="notice-dismiss"><span class="screen-reader-text">', esc_html__( 'Dismiss this notice.', 'mailchimp-for-wp' ), '</span></button><input type="hidden" name="_mc4wp_action" value="dismiss_review_notice" />', wp_nonce_field( '_mc4wp_action', '_wpnonce', true, false ), '</form>';
 		echo '</div>';
 		return true;
 	}