Merge pull request #6574 from ampproject/fix/2.1-build-error-for-tiktok

[2.1] Use string literal for amp-tiktok instead of constant until amp-toolbox updated

includes/embeds/class-amp-tiktok-embed-handler.php

@@ -8,7 +8,6 @@
 use AmpProject\Attribute;
 use AmpProject\Dom\Document;
 use AmpProject\Dom\Element;
-use AmpProject\Extension;
 use AmpProject\Layout;
 use AmpProject\Tag;
 
@@ -40,7 +39,7 @@ public function unregister_embed() {
 	 */
 	public function sanitize_raw_embeds( Document $dom ) {
 		$nodes = $dom->xpath->query(
-			sprintf( '//blockquote[ @cite and @data-video-id and contains( @class, "tiktok-embed" ) and not( parent::%s ) ]', Extension::TIKTOK )
+			sprintf( '//blockquote[ @cite and @data-video-id and contains( @class, "tiktok-embed" ) and not( parent::%s ) ]', 'amp-tiktok' )
 		);
 
 		foreach ( $nodes as $node ) {
@@ -66,7 +65,7 @@ protected function make_embed_amp_compatible( Element $blockquote ) {
 
 		$amp_tiktok = AMP_DOM_Utils::create_node(
 			Document::fromNode( $dom ),
-			Extension::TIKTOK,
+			'amp-tiktok',
 			[
 				Attribute::LAYOUT   => Layout::RESPONSIVE,
 				Attribute::HEIGHT   => 575,