Deprecate then remove postsPerPage method

[joemaller]

Does not belong in the data-model, this should be set from the theme.

wp-data-model/src/CPT.php

Lines 73 to 96 in fbc1074

	/**
	* Reference: https://codex.wordpress.org/Plugin_API/Action_Reference/pre_get_posts#Changing_the_number_of_posts_per_page.2C_by_post_type
	*
	* Assignment hierarchy for posts_per_page:
	* 1. $query->query['per_page']
	* 2. $query->query['posts_per_page']
	* 3. $this->posts_per_page
	* 4. get_option('posts_per_page')
	*/
	public function postsPerPage($query)
	{
	if (
	!is_admin() &&
	!wp_is_json_request() &&
	isset($query->query_vars['post_type']) &&
	$query->query_vars['post_type'] == $this->type
	) {
	$per_page =
	$query->query['per_page'] ??
	($query->query['posts_per_page'] ??
	($this->posts_per_page ?? get_option('posts_per_page')));
	$query->set('posts_per_page', $per_page);
	}
	}