diff -up wordpress/wp-includes/script-loader.php.old wordpress/wp-includes/script-loader.php
--- wordpress/wp-includes/script-loader.php.old	2020-03-25 16:34:50.606199762 +0100
+++ wordpress/wp-includes/script-loader.php	2020-03-25 16:35:59.409883628 +0100
@@ -892,12 +892,6 @@ function wp_default_scripts( $scripts )
 	$scripts->add( 'wp-plupload', "/wp-includes/js/plupload/wp-plupload$suffix.js", array( 'plupload', 'jquery', 'json2', 'media-models' ), false, 1 );
 	did_action( 'init' ) && $scripts->localize( 'wp-plupload', 'pluploadL10n', $uploader_l10n );
 
-	// Keep 'swfupload' for back-compat.
-	$scripts->add( 'swfupload', '/wp-includes/js/swfupload/swfupload.js', array(), '2201-20110113' );
-	$scripts->add( 'swfupload-all', false, array( 'swfupload' ), '2201' );
-	$scripts->add( 'swfupload-handlers', "/wp-includes/js/swfupload/handlers$suffix.js", array( 'swfupload-all', 'jquery' ), '2201-20110524' );
-	did_action( 'init' ) && $scripts->localize( 'swfupload-handlers', 'swfuploadL10n', $uploader_l10n );
-
 	$scripts->add( 'comment-reply', "/wp-includes/js/comment-reply$suffix.js", array(), false, 1 );
 
 	$scripts->add( 'json2', "/wp-includes/js/json2$suffix.js", array(), '2015-05-03' );