Update default iframeSrc to be 'about:blank' in all cases

Author: KorvinSzanto

src/jquery.form.js

@@ -159,7 +159,7 @@
 			url       : url,
 			success   : $.ajaxSettings.success,
 			type      : method || $.ajaxSettings.type,
-			iframeSrc : /^https/i.test(window.location.href || '') ? 'javascript:false' : 'about:blank'		// eslint-disable-line no-script-url
+			iframeSrc : 'about:blank'
 		}, options);
 
 		// hook for manipulating the form data before it is extracted;