[Dependabot]: Bump com.diffplug.spotless from 7.0.3 to 8.1.0

Bumps com.diffplug.spotless from 7.0.3 to 8.1.0.

---
updated-dependencies:
- dependency-name: com.diffplug.spotless
  dependency-version: 8.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

build.gradle

@@ -8,7 +8,7 @@ plugins {
     // to make our tests output more fancy
     id 'com.adarshr.test-logger' version '4.0.0'
     // code linting
-    id "com.diffplug.spotless" version "7.0.3"
+    id "com.diffplug.spotless" version "8.1.0"
     //  test coverage
     id 'jacoco'
     id 'com.github.kt3k.coveralls' version '2.12.2'