Bump com.diffplug.spotless from 7.2.1 to 8.4.0

Bumps com.diffplug.spotless from 7.2.1 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-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -9,7 +9,7 @@ jmh = 'me.champeau.jmh:0.7.3'
 pitest = 'info.solidsoft.pitest:1.15.0'
 publish-plugin = 'io.github.gradle-nexus.publish-plugin:2.0.0'
 release = 'net.researchgate.release:3.1.0'
-spotless = 'com.diffplug.spotless:7.2.1'
+spotless = 'com.diffplug.spotless:8.4.0'
 
 [libraries]
 assertj = 'org.assertj:assertj-core:3.27.7'