Bump log4j.version from 2.14.1 to 2.15.0 (#27)

Bumps `log4j.version` from 2.14.1 to 2.15.0.

Updates `log4j-slf4j-impl` from 2.14.1 to 2.15.0

Updates `log4j-api` from 2.14.1 to 2.15.0

Updates `log4j-core` from 2.14.1 to 2.15.0

---
updated-dependencies:
- dependency-name: org.apache.logging.log4j:log4j-slf4j-impl
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.logging.log4j:log4j-api
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.apache.logging.log4j:log4j-core
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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flatmap-core/pom.xml

@@ -18,7 +18,7 @@
   <properties>
     <graphhopper.version>2.4</graphhopper.version>
     <geotools.version>26.1</geotools.version>
-    <log4j.version>2.14.1</log4j.version>
+    <log4j.version>2.15.0</log4j.version>
     <prometheus.version>0.12.0</prometheus.version>
   </properties>