[jdk21u] RFR: 8314495: Update to use jtreg 7.3.1

[Paul Hohensee]

On Fri, 1 Sep 2023 08:29:18 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Unclean backport to bring jtreg version in alignment with mainline. The uncleanliness comes from contextual difference re gtest version in the adjacent hunks.
> 
> Additional testing:
>  - [x] GHA

Marked as reviewed by phh (Reviewer).

-------------

PR Review: https://git.openjdk.org/jdk21u/pull/123#pullrequestreview-1607195617