Bump io.freefair.javadoc-utf-8 from 8.4 to 8.6

Bumps [io.freefair.javadoc-utf-8](https://github.com/freefair/gradle-plugins) from 8.4 to 8.6.
- [Release notes](https://github.com/freefair/gradle-plugins/releases)
- [Commits](freefair/gradle-plugins@8.4...8.6)

---
updated-dependencies:
- dependency-name: io.freefair.javadoc-utf-8
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

build.gradle.kts

@@ -11,7 +11,7 @@ plugins {
     id("org.cadixdev.licenser") version "0.6.1"
     id("me.qoomon.git-versioning") version "6.4.3"
     id("io.freefair.javadoc-links") version "8.4"
-    id("io.freefair.javadoc-utf-8") version "8.4"
+    id("io.freefair.javadoc-utf-8") version "8.6"
     id("com.github.ben-manes.versions") version "0.51.0"
     id("io.freefair.maven-central.validate-poms") version "8.4"
     id("ru.vyarus.pom") version "2.2.2"