RFR: 1216: Update to JDK 17 and Gradle 7.2

Wed Oct 13 21:41:47 UTC 2021

On Wed, 13 Oct 2021 21:20:00 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

> I have no objection if you want to update to gradle 7.2 and JDK 17 as long as you've done enough testing.
> 
> It looks like you missed updating [gradle/wrapper/gradle-wrapper.properties](https://github.com/openjdk/skara/blob/master/gradle/wrapper/gradle-wrapper.properties#L22).

Ah good catch. The gradle-wrapper.properties isn't used by the main gradlew script, but I suppose it's there to be picked up by IDEs.

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PR: https://git.openjdk.java.net/skara/pull/1235