RFR: 8321140: Add comment to note difference in Metal's JButton margins [v3]

[Harshitha Onkar]

On Fri, 16 Aug 2024 18:53:22 GMT, Damon Nguyen <dnguyen at openjdk.org> wrote:

>> I agree, adding a note at both places looks clearer. The additional note in MetalLookAndFeel.java as above gives a quick lookup.
>
> That does sound best. Added the notes to both areas as suggested. I still don't know how to not make the note in `MetalLookAndFeel.java` not feel like it's hanging, but I added the note to the same spot again. I think it's the most logical area.

LGTM, copyright years need to be updated for the files.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20482#discussion_r1720242318