How can I hide the Webpushr preview button in wordPress Plugin?

How can I hide the preview button on the post edit page?

Put this code into functions.php of your template:

add_action(‘admin_head’, ‘webpushr_hidden’);

function webpushr_hidden() {
echo ’
#webpushr_13fw3_switch-mode {
display: none;
}
';
}