Bump com.diffplug.spotless from 6.3.0 to 6.4.0

Bumps com.diffplug.spotless from 6.3.0 to 6.4.0.

---
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

@@ -20,7 +20,7 @@ buildscript {
 }
 
 plugins {
-    id 'com.diffplug.spotless' version '6.3.0'
+    id 'com.diffplug.spotless' version '6.4.0'
     id 'eclipse'
     id 'com.github.ben-manes.versions' version '0.42.0'
     id 'biz.aQute.bnd.builder' version '6.2.0'