Fix publications by excluding testFixturesApi components

[reta]

Fix publications by excluding testFixturesApi components. Those cause an invalid POM file being generated:

[WARNING] The POM for org.wiremock:wiremock:jar:3.5.1 is invalid, transitive dependencies (if any) will not be available: 3 problems were encountered while building the effective model for org.wiremock:wiremock:3.5.1

Verified locally with ./gradlew localRelease

References

Closes #2660

Submitter checklist

• Recommended: Join WireMock Slack to get any help in #help-contributing or a project-specific channel like #wiremock-java
• The PR request is well described and justified, including the body and the references
• The PR title represents the desired changelog entry
• The repository's code style is followed (see the contributing guide)
• Test coverage that demonstrates that the change works as expected
• For new features, there's necessary documentation in this pull request or in a subsequent PR to wiremock.org

[reta]

Referring to Gradle documentation here:

If you publish your library and use test fixtures, but do not want to publish the fixtures, you can deactivate publishing of the test fixtures variants as shown below. - https://docs.gradle.org/current/userguide/java_testing.html