Bump log4j-core from 2.13.3 to 2.15.0 in /parent-conf (#246)

Bumps log4j-core from 2.13.3 to 2.15.0.

---
updated-dependencies:
- dependency-name: org.apache.logging.log4j:log4j-core
  dependency-type: direct:production
...

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Author: dependabot[bot]