Update Dockerfile eclipse-temurin version

[bbezanson]

Update eclipse-temurin to v11.0.20_8-jre

eclipse-temurin has been updated to the newer JDK and contains security updates.

References

https://github.com/docker-library/docs/blob/master/eclipse-temurin/README.md#supported-tags-and-respective-dockerfile-links

Submitter checklist

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

[oleg-nenashev]

Just saw it. Right now the dependency management is not great, and many updates are needed. See #79