RFR: 8310999: Add @since info in jdk.jsobject files [v2]

[Iris Clark]

On Wed, 5 Jul 2023 16:20:07 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> Source code cleanup.
>> Add @since, remove unused imports and remove unnecessary SuppressWarnings of deprecation.
>
> Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove unneeded @SuppressWarnings

Marked as reviewed by iris (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/14775#pullrequestreview-1514905287