Bump mockserver.version from 5.15.0 to 6.0.0 (#1895)

Bumps `mockserver.version` from 5.15.0 to 6.0.0.

Updates `org.mock-server:mockserver-junit-jupiter` from 5.15.0 to 6.0.0

Updates `org.mock-server:mockserver-netty` from 5.15.0 to 6.0.0

---
updated-dependencies:
- dependency-name: org.mock-server:mockserver-junit-jupiter
  dependency-version: 6.0.0
  dependency-type: direct:development
  update-type: version-update:semver-major
- dependency-name: org.mock-server:mockserver-netty
  dependency-version: 6.0.0
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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