Bump spotless version to 5.6.1

Author: skydoves

dependencies.gradle

@@ -5,13 +5,13 @@ ext.versions = [
     versionName      : '2.2.0',
 
     gradleBuildTool  : '3.6.3',
-    spotlessGradle   : '5.3.0',
+    spotlessGradle   : '5.6.1',
     bintrayRelease   : '0.9.2',
 
     androidxAppcompat: '1.2.0',
 
     // for demo
-    googleMaterial   : '1.3.0-alpha01',
+    googleMaterial   : '1.3.0-alpha02',
     powermenu        : '2.1.3',
     timber           : '4.7.1'
 ]