RFR: 8348308: Make fields of ListSelectionEvent final

[Alexander Zvegintsev]

On Wed, 22 Jan 2025 20:20:28 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

> The fields of `ListSelectionEvent` are set in the constructor and are never modified, mark the fields — `firstIndex`, `lastIndex`, `isAdjusting` — with the `final` modifier.

Marked as reviewed by azvegint (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/23243#pullrequestreview-2569077165