chore: update Gradle to 9.7.0

[rasros]

Summary

Gradle 9.6.1 to 9.7.0, via ./gradlew wrapper --gradle-version 9.7.0 run twice so the wrapper jar
and scripts regenerate under the new version rather than only the properties file.

One new warning, and it is not ours

9.7.0 adds a deprecation that 9.6.1 did not report:

Using a Project object as a dependency notation has been deprecated.
This will fail with an error in Gradle 10.

The stack trace puts it inside Kover, not in any build script here:

at kotlinx.kover.gradle.plugin.appliers.PrepareKoverKt.prepare(PrepareKover.kt:29)
at kotlinx.kover.gradle.plugin.KoverGradlePlugin.apply(KoverGradlePlugin.kt:29)

Kover is applied by the com.eignex.kmp convention, so every repo using it reports this. 0.9.9 is
the newest Kover published, so there is nothing to bump to; it needs an upstream fix before Gradle
10. Builds pass, this is a warning today.

Worth noting the bump widens rather than closes the Kotlin compatibility gap: Kotlin 2.4.x is
tested against Gradle 7.6.3 to 9.5.0, so 9.6.1 was one minor out and 9.7.0 is two.

Testing

Gradle 9.7.0 downloads and runs (the second wrapper pass executes under it). jvmTest passes.