RFR: 7903499: Update various versions used by jtreg's IDEA plugin

[Christian Stein]

On Sat, 10 Jun 2023 18:00:16 GMT, Christoph <duke at openjdk.org> wrote:

> This enables building the plugin with never java versions
> 
> I tested with IntelliJ 2023.1.2 and java 17 and 19
> 
> Plugin still works

It's not the binary causing an issue, it's the executable bit in `plugins/idea/gradlew`. Please revert the file access modifiers - but keep the content.

Would you please update the Gradle version to 7.6.1 and include the SHA256 checksum of the Gradle Wrapper in the `gradle/wrapper/gradle-wrapper.properties` file? Find checksums here: https://gradle.org/release-checksums/

I'll address the "Commit message must refer to an issue" separately.

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PR Comment: https://git.openjdk.org/jtreg/pull/157#issuecomment-1597455287