Bump com.diffplug.spotless from 6.8.0 to 6.9.0 (#100)

Bumps com.diffplug.spotless from 6.8.0 to 6.9.0.

---
updated-dependencies:
- dependency-name: com.diffplug.spotless
  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>

Author: dependabot[bot]

settings.gradle

@@ -5,7 +5,7 @@ pluginManagement {
         id 'com.avast.gradle.docker-compose' version "0.16.8" apply false
         id 'io.gitlab.arturbosch.detekt' version "1.21.0" apply false
         id 'com.github.johnrengelman.shadow' version "7.1.2" apply false
-        id 'com.diffplug.spotless' version '6.8.0' apply false
+        id 'com.diffplug.spotless' version '6.9.0' apply false
     }
 }