RFR: 8372977: unnecessary gthread-2.0 loading

[Alexander Zuev]

On Wed, 3 Dec 2025 05:15:00 GMT, Alexander Zvegintsev <azvegint at openjdk.org> wrote:

> Actual usage of the gthread-2.0 was removed with GTK2 support in [JDK-8329471](https://bugs.openjdk.org/browse/JDK-8329471).
> But there are some leftovers, we are still loading it with GTK3, even though it was never used when it was added in [JDK-8164321](https://bugs.openjdk.org/browse/JDK-8164321).
> 
> It wasn't an issue before, but some modern systems (e.g. openSUSE 16) don't provide the library.
> Because of this, we are unable to load GTK, which leads to Robot functionality requiring the Screencast or Remote Desktop API on Wayland not working.

Looks good.

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

Marked as reviewed by kizune (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/28625#pullrequestreview-3536657795