#488: Change kotlinOptions.jvmTarget to VERSION_1_8

[naitaku]

This commit addresses issue #488, where Android projects were encountering a build failure with the error message: "Cannot inline bytecode built with JVM target 11."
The issue was resolved by adjusting the 'jvmTarget' to 'VERSION_1_8,' ensuring compatibility with Android projects.

• Can you back your code up with tests?

• Add mockito-kotlin dependency with testImplementation and androidTestImplementation to an Android project, and mock function works.

• Keep your commits clean: squash your commits if necessary.

[TimvdLippe]

Mockito 5 no longer supports Java 8. Therefore, I don't think we should do that for mockito-kotlin either, should we?

[naitaku]

My understanding is that mockito-core 5.x no longer supports Java 8, and 'jvmTarget' should be set to 'VERSION_11.'
I'll close this PR.