build(deps): Bump the dev-dependencies group with 2 updates (#5)

Bumps the dev-dependencies group with 2 updates: [com.diffplug.spotless:spotless-plugin-gradle](https://github.com/diffplug/spotless) and com.diffplug.spotless.


Updates `com.diffplug.spotless:spotless-plugin-gradle` from 7.2.1 to 8.4.0
- [Release notes](https://github.com/diffplug/spotless/releases)
- [Changelog](https://github.com/diffplug/spotless/blob/main/CHANGES.md)
- [Commits](diffplug/spotless@gradle/7.2.1...gradle/8.4.0)

Updates `com.diffplug.spotless` from 7.2.1 to 8.4.0

---
updated-dependencies:
- dependency-name: com.diffplug.spotless:spotless-plugin-gradle
  dependency-version: 8.4.0
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dev-dependencies
- dependency-name: com.diffplug.spotless
  dependency-version: 8.4.0
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: dev-dependencies
...

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Author: dependabot[bot]

gradle/libs.versions.toml

@@ -10,7 +10,7 @@
 java = "21"
 
 # Build / quality
-spotless = "7.2.1"
+spotless = "8.4.0"
 errorprone-plugin = "4.1.0"
 errorprone-core = "2.49.0"
 google-java-format = "1.25.2"