Using custom elements: make Safari implementation stance clear (mdn#3…

…6979)

* Using custom elements: make Safari implementation stance clear

* workaround linter

* Update index.md

* Remove links and point to `is` attribute instead

* change note marker back

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Co-authored-by: Brian Smith <brian@smith.berlin>

files/en-us/web/api/web_components/using_custom_elements/index.md

@@ -17,7 +17,7 @@ There are two types of custom element:
 - **Customized built-in elements** inherit from standard HTML elements such as {{domxref("HTMLImageElement")}} or {{domxref("HTMLParagraphElement")}}. Their implementation extends the behavior of select instances of the standard element.
 
   > [!NOTE]
-  > Please see the [`is`](/en-US/docs/Web/HTML/Global_attributes/is) attribute reference for caveats on implementation reality of custom built-in elements.
+  > Safari does not plan to support custom built-in elements. See the [`is` attribute](/en-US/docs/Web/HTML/Global_attributes/is) for more information.
 
 - **Autonomous custom elements** inherit from the HTML element base class {{domxref("HTMLElement")}}. You have to implement their behavior from scratch.