RFR: 8289006: Cleanup from thread.hpp split [v2]

[Coleen Phillimore]

On Thu, 23 Jun 2022 12:30:44 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Remove extra include directives.  Tested with GHA.
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   remove redundant include

Thanks Dan for the comments, and David for reviewing.  Pushing as trivial.

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PR: https://git.openjdk.org/jdk/pull/9252