Set og:image to the existing wp.org/news image on Make posts

[claytoncollie]

In reference to https://meta.trac.wordpress.org/ticket/975

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This is what it looks like for posts from ​https://make.wordpress.org/core

​https://socialsharepreview.com/?url=https://make.wordpress.org/core/2020/08/26/wordpress-5-5-1-maintenance-release-schedule/

This is what it looks like for posts from ​https://wordpress.org/news

​https://socialsharepreview.com/?url=https://wordpress.org/news/2020/10/the-month-in-wordpress-september-2020/

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Can use the images from [975](https://meta.trac.wordpress.org/ticket/975) to make the default image consistent?

[dd32]

In 10462:

Open-source the Jetpack mu-plugin we use to tweak the default og:image and Twitter site names.

See #975, #5475.

[dd32]

Jetpack was inheriting the "Site Icon" preference from the customizer, I don't think it was actually being used for anything specifically so I've removed it in favour of the default images that the mu-plugin offers.

I've open-sourced that mu-plugin since I was looking into this code and it was in the private repo.

It looks like the Site Icon functionality was only offering higher-resolution non-favicon images:

<link rel="icon" href="https://make.wordpress.org/core/files/2015/11/wordpress-logo-notext-rgb-150x150.png" sizes="32x32" />
<link rel="icon" href="https://make.wordpress.org/core/files/2015/11/wordpress-logo-notext-rgb-300x300.png" sizes="192x192" />
<link rel="apple-touch-icon" href="https://make.wordpress.org/core/files/2015/11/wordpress-logo-notext-rgb-300x300.png" />
<meta name="msapplication-TileImage" content="https://make.wordpress.org/core/files/2015/11/wordpress-logo-notext-rgb-300x300.png" />

It's probably worthwhile migrating that from per-site settings to the global WordPress.org header (which currently only references favicon.ico) rather than just removing these tags outright.