DOMElement insertAdjacentElement should not be pure. (#11333)

std/js/html/DOMElement.hx

@@ -391,7 +391,6 @@ extern class DOMElement extends Node {
 		Inserts a given element node at a given position relative to the element it is invoked upon.
 		@throws DOMError
 	**/
-	@:pure
 	function insertAdjacentElement( where : String, element : Element ) : Element;
 	
 	/**
@@ -550,4 +549,4 @@ extern class DOMElement extends Node {
 	/** @throws DOMError */
 	@:overload( function( nodes : haxe.extern.Rest<String>) : Void {} )
 	function append( nodes : haxe.extern.Rest<Node> ) : Void;
-}
+}