Remove unnecessary dynamic meta key

Fixes #24

assets/build/gutenberg.asset.php

-<?php return array('dependencies' => array('wp-api-fetch', 'wp-components', 'wp-compose', 'wp-data', 'wp-edit-post', 'wp-element', 'wp-i18n', 'wp-plugins'), 'version' => '4fb62ef836a783d428cc');
+<?php return array('dependencies' => array('wp-api-fetch', 'wp-components', 'wp-compose', 'wp-data', 'wp-edit-post', 'wp-element', 'wp-i18n', 'wp-plugins'), 'version' => 'bd5ae5b661174c1a9835');