RFR: 8366369: Add @requires linux for GTK L&F tests

[Tejesh R]

On Thu, 28 Aug 2025 18:34:00 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

> * Add `@requires os.family == "linux"` to prevent GTK L&F tests from running on other OS but Linux.
> * Let any exceptions from `UIManager.setLookAndFeel` propagate.
> * Remove `@author` tag.
> * Expand imports in `test/jdk/com/sun/java/swing/plaf/gtk/Test6635110.java`.
> * Add leading asterisks to jtreg comment block.

LGTM

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Marked as reviewed by tr (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26995#pullrequestreview-3175455311