Apply suggestion for colgroup element

Co-authored-by: Estelle Weyl <[email protected]>

files/en-us/web/html/element/colgroup/index.md

@@ -53,7 +53,7 @@ The following attributes are deprecated and should not be used. They are documen
 
     > **Note:** Setting `vertical-align` on the `<colgroup>` element has no effect as {{HTMLElement("td")}} and {{HTMLElement("th")}} elements are not descendants of the `<colgroup>` element, and therefore they do not inherit from it.
     >
-    > If the table does not use a [`colspan`](/en-US/docs/Web/HTML/Element/td#colspan) attribute, use the `td:nth-of-type(an+b)` CSS selector per column, where `a` is the total number of the columns in the table and `b` is the ordinal position of the column in the table, e.g. `td:nth-of-type(7n+2) { vertical-align: middle; }` to center the second column cells vertically.
+    > If the table does not use a [`colspan`](/en-US/docs/Web/HTML/Element/td#colspan) attribute, use the [`td:nth-of-type()`](/en-US/docs/Web/CSS/:nth-of-type) CSS selector per column, e.g. `td:nth-of-type(2) { vertical-align: middle; }` to center the second column cells vertically.
     >
     > If the table does use a [`colspan`](/en-US/docs/Web/HTML/Element/td#colspan) attribute, the effect can be achieved by combining adequate CSS attribute selectors like `[colspan=n]`, though this is not trivial.