Merge pull request #441 from yuzawa-san/dependabot/gradle/com.diffplug.spotless-8.9.0

Bump com.diffplug.spotless from 8.8.0 to 8.9.0

Author: yuzawa-san

build.gradle

@@ -1,5 +1,5 @@
 plugins {
-	id "com.diffplug.spotless" version "8.8.0"
+	id "com.diffplug.spotless" version "8.9.0"
 	id 'java'
 	id 'maven-publish'
 	id 'signing'