docs: remove 404 link (#1683) [ci skip]

docs/guide/scoped-css.md

@@ -70,6 +70,6 @@ DOM content created with `v-html` are not affected by scoped styles, but you can
 
 ## Also Keep in Mind
 
-- **Scoped styles do not eliminate the need for classes**. Due to the way browsers render various CSS selectors, `p { color: red }` will be many times slower when scoped (i.e. when combined with an attribute selector). If you use classes or ids instead, such as in `.example { color: red }`, then you virtually eliminate that performance hit. [Here's a playground](https://stevesouders.com/efws/css-selectors/csscreate.php) where you can test the differences yourself.
+- **Scoped styles do not eliminate the need for classes**. Due to the way browsers render various CSS selectors, `p { color: red }` will be many times slower when scoped (i.e. when combined with an attribute selector). If you use classes or ids instead, such as in `.example { color: red }`, then you virtually eliminate that performance hit. 
 
 - **Be careful with descendant selectors in recursive components!** For a CSS rule with the selector `.a .b`, if the element that matches `.a` contains a recursive child component, then all `.b` in that child component will be matched by the rule.