deps: bump net.kyori:adventure-api from 4.20.0 to 4.21.0 (#520)

Bumps [net.kyori:adventure-api](https://github.com/KyoriPowered/adventure) from 4.20.0 to 4.21.0.
- [Release notes](https://github.com/KyoriPowered/adventure/releases)
- [Commits](https://github.com/KyoriPowered/adventure/compare/v4.20.0...v4.21.0)

---
updated-dependencies:
- dependency-name: net.kyori:adventure-api
  dependency-version: 4.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

common/build.gradle

@@ -23,7 +23,7 @@ dependencies {
     compileOnly 'com.mojang:brigadier:1.1.8'
     compileOnly 'org.projectlombok:lombok:1.18.38'
     compileOnly 'org.jetbrains:annotations:26.0.2'
-    compileOnly 'net.kyori:adventure-api:4.20.0'
+    compileOnly 'net.kyori:adventure-api:4.21.0'
     compileOnly 'net.kyori:adventure-platform-api:4.4.0'
     compileOnly "net.kyori:adventure-text-serializer-plain:4.21.0"
     compileOnly 'com.google.guava:guava:33.4.8-jre'