Bump checkstyle

Author: JRoy

build-logic/src/main/kotlin/essentials.base-conventions.gradle.kts

@@ -9,7 +9,7 @@ plugins {
 
 val baseExtension = extensions.create<EssentialsBaseExtension>("essentials", project)
 
-val checkstyleVersion = "8.36.2"
+val checkstyleVersion = "9.2.1"
 val spigotVersion = "1.18.1-R0.1-SNAPSHOT"
 val junit5Version = "5.7.0"
 val mockitoVersion = "3.2.0"