PHP is not a valid `lang` value, used on source code blocks

[adamwoodnz]

          PHP is not a valid `lang` value, used on source code blocks

Originally posted by @adamwoodnz in #179 (comment)

[ryelle]

Looks like this is coming from Code Syntax Block, and there's a PR mkaz/code-syntax-block#85 … which is maybe blocked upstream 🙃

This affects all sites using the Code Syntax Block (which might just be this one & the developer blog), so we should probably drop something in wporg-mu-plugins to fix it. Something like this would work, even if it's hacky.

add_filter(
	'render_block_core/code',
	function( $block_content ) {
		// Only replaces php, but other sites use javascript and others, so ideally this would catch all.
		return str_replace( 'lang="php"', '', $block_content );
	}
);