RFR: JDK-8329004 : Update Libpng to 1.6.43 [v3]

[Phil Race]

On Thu, 25 Apr 2024 23:17:59 GMT, Harshitha Onkar <honkar at openjdk.org> wrote:

>> Libpng updated from 1.6.40 to  1.6.43
>
> Harshitha Onkar has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Updating.txt

Marked as reviewed by prr (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/18964#pullrequestreview-2025736301