Update google-java-format version to 1.6

Change-Id: I32a8368d93f4d574f24f7d66f4893f280bc90a3e

Author: vkryachko

root-project.gradle

@@ -53,6 +53,9 @@ configure(subprojects) {
     }
     apply plugin: 'net.ltgt.errorprone'
     apply plugin: 'com.github.sherter.google-java-format'
+    googleJavaFormat {
+        toolVersion = '1.6'
+    }
     tasks.googleJavaFormat {
         source '.'
         include '**/*.java'