chore(showcase): Remove sites from showcase (#22541)
chore(showcase): Remove sites from showcase (#22541)

Remove deepThreads: Site no longer routing to a valid site
Remove danieljs.tech source_url
Remove Patrik Arvidsson's portfolio: Site switched to Next
Remove yerevancoder: Site no longer online (and username on github has dissapeared)
Remove Pravdomil: Site no longer built with Gatsby
Remove William Owen UK Portfolio / Blog: Site not online anymore
Remove Hubba: specific URL no longer routing and main site is just React and not Gatsby
Remove justaskusers.com: Site no longer online
gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby,gatsbyjs/gatsby