RFR: 8365711: Declare menuBarHeight and hotTrackingOn private

[Alexander Zuev]

On Mon, 18 Aug 2025 17:05:26 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

> Since `WindowsMenuUI` is a final class after PR #24170 for [JDK-8352638](https://bugs.openjdk.org/browse/JDK-8352638)), it cannot be extended, therefore the `protected` modifier doesn't make sense.
> 
> Mark both `menuBarHeight` and `hotTrackingOn` as `private` fields.

Marked as reviewed by kizune (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/26829#pullrequestreview-3141422180