Bump com.diffplug.spotless:spotless-plugin-gradle to 6.20.0 (#3401)

Bumps [com.diffplug.spotless:spotless-plugin-gradle](https://github.com/diffplug/spotless) from 6.19.0 to 6.20.0.
- [Changelog](https://github.com/diffplug/spotless/blob/main/CHANGES.md)
- [Commits](diffplug/spotless@gradle/6.19.0...gradle/6.20.0)

---
updated-dependencies:
- dependency-name: com.diffplug.spotless:spotless-plugin-gradle
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Author: dependabot[bot]

gradle/libs.versions.toml

@@ -36,7 +36,7 @@ gradle-foojayResolver = { module = "org.gradle.toolchains:foojay-resolver", vers
 gradle-enterprise = { module = "com.gradle:gradle-enterprise-gradle-plugin", version = "3.14" }
 gradle-bnd = { module = "biz.aQute.bnd:biz.aQute.bnd.gradle", version.ref = "bnd" }
 gradle-shadow = { module = "com.github.johnrengelman:shadow", version = "8.1.1" }
-gradle-spotless = { module = "com.diffplug.spotless:spotless-plugin-gradle", version = "6.19.0" }
+gradle-spotless = { module = "com.diffplug.spotless:spotless-plugin-gradle", version = "6.20.0" }
 gradle-versions = { module = "com.github.ben-manes:gradle-versions-plugin", version.ref = "gradleVersionsPlugin" }
 groovy4 = { module = "org.apache.groovy:groovy", version = "4.0.13" }
 groovy2-bom = { module = "org.codehaus.groovy:groovy-bom", version = "2.5.21" }