Bump com.diffplug.spotless from 8.2.1 to 8.4.0 in /lib/kotlin

Bumps com.diffplug.spotless from 8.2.1 to 8.4.0.

---
updated-dependencies:
- dependency-name: com.diffplug.spotless
  dependency-version: 8.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/lib/java/build.gradle b/lib/java/build.gradle
index 7dbca24..d1ca654 100644
--- a/lib/java/build.gradle
+++ b/lib/java/build.gradle
@@ -42,7 +42,7 @@
     id 'pmd'
     id 'com.github.johnrengelman.shadow' version '8.1.1'
     id "com.github.spotbugs" version "5.2.5"
-    id "com.diffplug.spotless" version "8.2.1"
+    id "com.diffplug.spotless" version "8.4.0"
 }
 
 description = 'Apache Thrift Java Library'