Udpate KtFmtStep to the new latest version.

Author: nedtwigg

lib/src/main/java/com/diffplug/spotless/kotlin/KtfmtStep.java

@@ -39,7 +39,7 @@ public class KtfmtStep {
 	// prevent direct instantiation
 	private KtfmtStep() {}
 
-	private static final String DEFAULT_VERSION = "0.39";
+	private static final String DEFAULT_VERSION = "0.40";
 	static final String NAME = "ktfmt";
 	static final String PACKAGE = "com.facebook";
 	static final String MAVEN_COORDINATE = PACKAGE + ":ktfmt:";