Increase visibility of Mockito dependency

[TWiStErRob]

• Fixes Regression in 5.2.0 POM: missing Mockito dependency for compilation #497

Thank you for submitting a pull request! But first:

• Can you back your code up with tests? See Update integration test to prevent regression #499
• Keep your commits clean: squash your commits if necessary.

[TWiStErRob]

Testing: gradlew publishToMavenLocal on main and on branch.
Diff ~\.m2\org\mockito\kotlin\mockito-kotlin\5.2.0 folder contents.
Expected: what's described in #497, actual: pass.