build(deps): bump org.mapstruct:mapstruct in /modules/gs-tree (#848)

Bumps [org.mapstruct:mapstruct](https://github.com/mapstruct/mapstruct) from 1.5.5.Final to 1.6.0.
- [Release notes](https://github.com/mapstruct/mapstruct/releases)
- [Commits](mapstruct/mapstruct@1.5.5.Final...1.6.0)

---
updated-dependencies:
- dependency-name: org.mapstruct:mapstruct
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

modules/gs-tree/pom.xml

@@ -101,7 +101,7 @@
  <dependency>
  <groupId>org.mapstruct</groupId>
  <artifactId>mapstruct</artifactId>
- <version>1.5.5.Final</version>
+ <version>1.6.0</version>
  </dependency>
  <dependency>
  <groupId>com.graphql-java-kickstart</groupId>