Upgrade Spotless Gradle plugin from 8.0.0 to 8.4.0 (#21023)

Signed-off-by: Andrew Ross <andrross@amazon.com>

Author: andrross

build.gradle

@@ -55,7 +55,7 @@ plugins {
   id 'lifecycle-base'
   id 'opensearch.docker-support'
   id 'opensearch.global-build-info'
-  id "com.diffplug.spotless" version "8.0.0" apply false
+  id "com.diffplug.spotless" version "8.4.0" apply false
   id "org.gradle.test-retry" version "1.6.2" apply false
   id "test-report-aggregation"
   id 'jacoco-report-aggregation'