External Libraries: Revert the change to the tb_click() function in the Thickbox library.

The `blur()` method there is not the jQuery method, but is an HTML DOM method instead.

This makes the Close button on the "View details" modal on Plugins screen functional again.

Follow-up to [50367].

Props afragen.
See #51812.

git-svn-id: https://develop.svn.wordpress.org/trunk@50383 602fd350-edb4-49c9-b593-d223f7449a82

src/js/_enqueues/vendor/thickbox/thickbox.js

@@ -35,7 +35,7 @@ function tb_click(){
 	var a = this.href || this.alt;
 	var g = this.rel || false;
 	tb_show(t,a,g);
-	this.trigger( 'blur' );
+	this.blur();
 	return false;
 }