git: openjdk/jdk: 8310259: Pin msys2/setup-msys2 github action to a specific commit

[Jaikiran Pai]

Changeset: 959a61fd
Author:    Jaikiran Pai <jpai at openjdk.org>
Date:      2023-06-17 06:02:40 +0000
URL:       https://git.openjdk.org/jdk/commit/959a61fdd483c9523764b9ba0972f59ca06db0ee

8310259: Pin msys2/setup-msys2 github action to a specific commit

Reviewed-by: cstein, stuefe

! .github/actions/get-jtreg/action.yml
! .github/actions/get-msys2/action.yml