Update web-components.md (#2333)

Updated custom-elements-es5-adapter link. Pointed to a repo that has moved.

content/docs/web-components.md

@@ -59,4 +59,4 @@ customElements.define('x-search', XSearch);
 >Note:
 >
 >This code **will not** work if you transform classes with Babel. See [this issue](https://github.com/w3c/webcomponents/issues/587) for the discussion.
->Include the [custom-elements-es5-adapter](https://github.com/webcomponents/webcomponentsjs#custom-elements-es5-adapterjs) before you load your web components to fix this issue.
+>Include the [custom-elements-es5-adapter](https://github.com/webcomponents/polyfills/tree/master/packages/webcomponentsjs#custom-elements-es5-adapterjs) before you load your web components to fix this issue.