RFR: 8297984: Turn on warnings as errors for javadoc

Fri Dec 2 03:38:09 UTC 2022

On Thu, 1 Dec 2022 22:20:00 GMT, Magnus Ihse Bursie <ihse at openjdk.org> wrote:

> For some reason, we never turned on `-Werror` for javadoc. It is high time to do so.
> 
> This PR also fixes a recent issue with the javadoc in JFR that caused a warning, and enables building of javadoc on GHA. (It takes about 3 minutes, as a separate build job.)

LGTM

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Marked as reviewed by serb (Reviewer).

PR: https://git.openjdk.org/jdk/pull/11468