RFR: 8332100: Add missing `@since` to KeyValue::EC_TYPE in `java.xml.crypto`

[Sean Mullan]

On Sat, 11 May 2024 15:46:20 GMT, Nizar Benalla <duke at openjdk.org> wrote:

> Simple code cleanup. I split my changes into 1 PR per module to make reviewing simpler.
> This was added back in [JDK 13](https://github.com/openjdk/jdk/commit/71825293eb83d7c9ac122c11a12465c2acbec040) and should have an `@since`
> If you're reviewing this change, thanks!

Marked as reviewed by mullan (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/19190#pullrequestreview-2052597313