refactor($sanitize): remove <script> from valid block elements

the script and style tag are explicitly blacklisted, so this doesn't change any functionality.
the change is done to improve code clarity.

Closes #12524

Author: IgorMinar

src/ngSanitize/sanitize.js

@@ -229,7 +229,7 @@ var optionalEndTagBlockElements = toMap("colgroup,dd,dt,li,p,tbody,td,tfoot,th,t
 // Safe Block Elements - HTML5
 var blockElements = angular.extend({}, optionalEndTagBlockElements, toMap("address,article," +
         "aside,blockquote,caption,center,del,dir,div,dl,figure,figcaption,footer,h1,h2,h3,h4,h5," +
-        "h6,header,hgroup,hr,ins,map,menu,nav,ol,pre,script,section,table,ul"));
+        "h6,header,hgroup,hr,ins,map,menu,nav,ol,pre,section,table,ul"));
 
 // Inline Elements - HTML5
 var inlineElements = angular.extend({}, optionalEndTagInlineElements, toMap("a,abbr,acronym,b," +