Posts, Post Types: Return early from `WP_Posts_List_Table::formats_dropdown()`...

Posts, Post Types: Return early from `WP_Posts_List_Table::formats_dropdown()` if the post type does not support post formats.

This avoids an unnecessary database query for the `post_format` taxonomy.

Props Chouby.
Fixes #50496.
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git-svn-id: https://core.svn.wordpress.org/trunk@47972 1a063a9b-81f0-0310-95a4-ce76da25c4cd