Update spotless packages to v8.4.0 (#2713)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

buildSrc/build.gradle.kts

@@ -1,7 +1,7 @@
 plugins {
   `kotlin-dsl`
   // When updating, update below in dependencies too
-  id("com.diffplug.spotless") version "8.3.0"
+  id("com.diffplug.spotless") version "8.4.0"
 }
 
 repositories {
@@ -12,7 +12,7 @@ repositories {
 
 dependencies {
   // When updating, update above in plugins too
-  implementation("com.diffplug.spotless:com.diffplug.spotless.gradle.plugin:8.3.0")
+  implementation("com.diffplug.spotless:com.diffplug.spotless.gradle.plugin:8.4.0")
   implementation("net.ltgt.errorprone:net.ltgt.errorprone.gradle.plugin:5.1.0")
   implementation("net.ltgt.nullaway:net.ltgt.nullaway.gradle.plugin:3.0.0")
   implementation("org.sonatype.gradle.plugins:scan-gradle-plugin:3.1.4")