1.3.0-beta04-dev873

Remove JVM target version override (#2515)

Previously, we were setting kotlin.jvmTarget version
to 1.8 if it was null or < 1.8.
As an unintended consequence we were also overriding
a version set by the jvmToolchain property.
So while users expected the jvmToolchain property
to set both jdk home & jdk target, we were quietly
overriding jdk target.

At the same time, Kotlin 1.7 sets the minimum
target version to 1.8 anyway, so our override
does not make sense with Kotlin 1.7+.

This commit removes overriding altogether.

Fixes #2511