Bump neo4j.version from 5.12.0 to 5.15.0

Bumps `neo4j.version` from 5.12.0 to 5.15.0.

Updates `org.neo4j:neo4j` from 5.12.0 to 5.15.0
- [Release notes](https://github.com/neo4j/neo4j/releases)
- [Commits](neo4j/neo4j@5.12.0...5.15.0)

Updates `org.neo4j.test:neo4j-harness` from 5.12.0 to 5.15.0
- [Release notes](https://github.com/neo4j/neo4j/releases)
- [Commits](neo4j/neo4j@5.12.0...5.15.0)

---
updated-dependencies:
- dependency-name: org.neo4j:neo4j
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.neo4j.test:neo4j-harness
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

pom.xml

@@ -17,7 +17,7 @@
 
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
-    <neo4j.version>5.12.0</neo4j.version>
+    <neo4j.version>5.15.0</neo4j.version>
     <neo4j-java-driver.version>5.12.0</neo4j-java-driver.version>
     <junit-jupiter.version>5.10.0</junit-jupiter.version>
     <maven-shade-plugin.version>3.5.1</maven-shade-plugin.version>