Doc block for hook_update_N is not displayed

Changing to Critical because this is a "Significant regressions in user experience, developer experience, or documentation".

If I weren't paid to fix this I would kick this back to the core queue saying stop writing documentation for phpcs and start writing documentation for developers but as is, I will of course fix it but I couldn't resist noting this.

Code looks good. The tests failure is just counts, which I think it's fixed in another MR.

Let's fix the fails/counts here.

Rebased and fixed the tests/counts.

Merged. Thanks.

Automatically closed - issue fixed for 2 weeks with no activity.