build(deps-dev): bump ch.qos.logback:logback-classic

Bumps [ch.qos.logback:logback-classic](https://github.com/qos-ch/logback) from 1.5.20 to 1.5.21.
- [Release notes](https://github.com/qos-ch/logback/releases)
- [Commits](qos-ch/logback@v_1.5.20...v_1.5.21)

---
updated-dependencies:
- dependency-name: ch.qos.logback:logback-classic
  dependency-version: 1.5.21
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

documentation/pom.xml

@@ -14,7 +14,7 @@
     <properties>
         <site.dir>${project.build.directory}/generated-docs/</site.dir>
         <format.skip>true</format.skip>
-        <logback-classic.version>1.5.20</logback-classic.version>
+        <logback-classic.version>1.5.21</logback-classic.version>
     </properties>
 
     <dependencies>