git: openjdk/jdk17u-dev: 8310259: Pin msys2/setup-msys2 github action to a specific commit

[Goetz Lindenmaier]

Changeset: 2b8c2600
Author:    Goetz Lindenmaier <goetz at openjdk.org>
Date:      2023-07-13 11:32:37 +0000
URL:       https://git.openjdk.org/jdk17u-dev/commit/2b8c260043f975807b403d1d7c52ac539d39502f

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

Reviewed-by: mbaesken
Backport-of: 959a61fdd483c9523764b9ba0972f59ca06db0ee

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