Update dependency com.diffplug.spotless:spotless-plugin-gradle to v6.18.0

Author: renovate[bot]

buildSrc/build.gradle.kts

@@ -35,7 +35,7 @@ repositories {
 dependencies {
     implementation("org.jetbrains.kotlinx:kotlinx-benchmark-plugin:0.4.7")
     implementation("org.jetbrains.kotlinx:atomicfu-gradle-plugin:0.18.5")
-    implementation("com.diffplug.spotless:spotless-plugin-gradle:6.12.0")
+    implementation("com.diffplug.spotless:spotless-plugin-gradle:6.18.0")
     implementation("org.jetbrains.dokka:dokka-gradle-plugin:1.7.20")
     implementation("dev.floofy.commons:gradle:2.4.1")
     implementation(kotlin("serialization", "1.7.22"))