RFR: 8306329 : Update ICU4C to 73.1 [v4]

[Johan Vos]

On Thu, 18 May 2023 17:22:46 GMT, Hima Bindu Meda <hmeda at openjdk.org> wrote:

>> Updated ICU to v73.1. Verified build and sanity. No issues seen.
>
> Hima Bindu Meda has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update preamble in LICENSE

Buld + tests ok

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Marked as reviewed by jvos (Reviewer).

PR Review: https://git.openjdk.org/jfx/pull/1138#pullrequestreview-1441116324