Backport #29121.

Remove https://glyph.smarticons.co/ from list of suggestions.
The domain is now for sale and is triggers warnings in Firefox and Chrome

site/docs/4.3/extend/icons.md

@@ -24,5 +24,4 @@ While we haven't tried these out, they do look promising and provide multiple fo
 - [Ionicons](https://ionicons.com/)
 - [Dripicons](http://demo.amitjakhu.com/dripicons/)
 - [Ikons](http://ikons.piotrkwiatkowski.co.uk/)
-- [Glyph](https://glyph.smarticons.co/)
 - [Icons8](https://icons8.com/)