Update plugin spotless to v6.18.0 (#32)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

gradle/libs.versions.toml

@@ -11,6 +11,6 @@ annotationsapi = { module = "org.apache.tomcat:annotations-api", version = "6.0.
 terminable = { module = "tr.com.infumia:terminable", version = "0.1.3" }
 
 [plugins]
-spotless = { id = "com.diffplug.spotless", version = "6.17.0" }
+spotless = { id = "com.diffplug.spotless", version = "6.18.0" }
 protobuf = { id = "com.google.protobuf", version = "0.9.2" }
 nexus = { id = "io.github.gradle-nexus.publish-plugin", version = "1.3.0" }