The `$response` parameter is an object, not an array.
This is a minor inconsistency with the corresponding `in_theme_update_message-{$theme_key}` action for themes, where the `$response` parameter is an array.
For backward compatibility, it is safer not to change the parameter type at this point, but to make sure the documentation is correct.
Follow-up to [11193], [16141], [26540].
Props davidmosterd, audrasjb, SergeyBiryukov.
See #40006.
Built from https://develop.svn.wordpress.org/trunk@51733
git-svn-id: http://core.svn.wordpress.org/trunk@51341 1a063a9b-81f0-0310-95a4-ce76da25c4cd
5a7eca9a0e