Bump Nexus publishing plugin to latest stable

[TWiStErRob]

Fixes build warning:

The org.gradle.util.ConfigureUtil type has been deprecated. This is scheduled to be removed in Gradle 9.0. Consult the upgrading guide for further information: https://docs.gradle.org/8.1/userguide/upgrading_version_7
.html#org_gradle_util_reports_deprecations
        at build_b11jx6juucrpzzoteqaolbrqh$_run_closure4.doCall(P:\projects\contrib\github-mockito-kotlin\build.gradle:41)
        (Run with --stacktrace to get the full stack trace of this deprecation warning.)

Thank you for submitting a pull request! But first:

• Can you back your code up with tests?
• Keep your commits clean: squash your commits if necessary.

Manual testing: gradlew publishToMavenLocal produced the same artifacts. + Nexus Publish Plugin follows semantic versioning, release notes don't contain any known breaking changes: https://github.com/gradle-nexus/publish-plugin/releases