Adapt <audio> test as we strip IE conditional comments

tests/php/test-amp-audio-converter.php

@@ -145,6 +145,7 @@ public function get_data() {
 			],
 
 			'audio_block_and_shortcode_output' => [
+			    // Note: the IE conditional comment is stripped, as AMP doesn't support those browsers anyway.
 				'
 					<figure class="wp-block-audio">
 						<audio controls src="https://wordpressdev.lndo.site/content/uploads/2019/02/do-you-know-I-am-batman.mp3"></audio>
@@ -168,7 +169,6 @@ public function get_data() {
 						<figcaption>Caption</figcaption>
 					</figure>
 
-					<!--[if lt IE 9]><script>document.createElement(\'audio\');</script><![endif]-->
 					<amp-audio class="wp-audio-shortcode amp-wp-199b6f0" id="audio-87-1" preload="none" controls="controls" width="auto">
 						<source type="audio/mpeg" src="https://wordpressdev.lndo.site/content/uploads/2019/02/do-you-know-I-am-batman.mp3?_=1">
 						<a href="https://wordpressdev.lndo.site/content/uploads/2019/02/do-you-know-I-am-batman.mp3" fallback="">https://wordpressdev.lndo.site/content/uploads/2019/02/do-you-know-I-am-batman.mp3</a>