Bump de.siegmar:logback-gelf from 5.0.+ to 6.1.1

Bumps [de.siegmar:logback-gelf](https://github.com/osiegmar/logback-gelf) from 5.0.+ to 6.1.1.
- [Release notes](https://github.com/osiegmar/logback-gelf/releases)
- [Changelog](https://github.com/osiegmar/logback-gelf/blob/master/CHANGELOG.md)
- [Upgrade guide](https://github.com/osiegmar/logback-gelf/blob/master/UPGRADE.md)
- [Commits](https://github.com/osiegmar/logback-gelf/commits/v6.1.1)

---
updated-dependencies:
- dependency-name: de.siegmar:logback-gelf
  dependency-version: 6.1.1
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

build.gradle

@@ -80,7 +80,7 @@ dependencies {
     compileOnly group: 'com.squareup.okhttp3', name: 'logging-interceptor', version: '4.12.0'
 
     // https://mvnrepository.com/artifact/de.siegmar/logback-gelf
-    compileOnly group: 'de.siegmar', name: 'logback-gelf', version: '5.0.+'
+    compileOnly group: 'de.siegmar', name: 'logback-gelf', version: '6.1.+'
 
     // https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-web
     testImplementation group: 'org.springframework.boot', name: 'spring-boot-starter-web', version: "${springBootVersion}"