fix(curriculum): use CSSHelper for grid-template-columns (#43982)

curriculum/challenges/english/01-responsive-web-design/css-grid/add-columns-with-grid-template-columns.md

@@ -29,11 +29,7 @@ Give the grid container three columns that are each `100px` wide.
 `container` class should have a `grid-template-columns` property with three units of `100px`.
 
 ```js
-assert(
-  code.match(
-    /.container\s*?{[\s\S]*grid-template-columns\s*?:\s*?100px\s*?100px\s*?100px\s*?;[\s\S]*}/gi
-  )
-);
+assert(new __helpers.CSSHelp(document).getStyle('.container')?.gridTemplateColumns === '100px 100px 100px');
 ```
 
 # --seed--