Bump com.diffplug.spotless from 6.19.0 to 6.20.0

Bumps com.diffplug.spotless from 6.19.0 to 6.20.0.

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

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

build.gradle

@@ -54,7 +54,7 @@ plugins {
   id 'lifecycle-base'
   id 'opensearch.docker-support'
   id 'opensearch.global-build-info'
-  id "com.diffplug.spotless" version "6.19.0" apply false
+  id "com.diffplug.spotless" version "6.20.0" apply false
   id "org.gradle.test-retry" version "1.5.4" apply false
   id "test-report-aggregation"
   id 'jacoco-report-aggregation'