Remove Validation.oldRuntime property

Author: alexander-yevsyukov

buildSrc/src/main/kotlin/io/spine/dependency/local/Validation.kt

@@ -53,9 +53,6 @@ object Validation {
     fun runtime(version: String) = "$runtimeModule:$version"
     val runtime = runtime(version)
 
-    @Deprecated("Use `runtime` instead.", ReplaceWith("runtime"))
-    const val oldRuntime = "io.spine.validation:spine-validation-java-runtime:2.0.0-SNAPSHOT.354"
-
     const val javaModule = "$group:$prefix-java"
     const val java = "$javaModule:$version"
     const val javaBundleModule = "$group:$prefix-java-bundle"