update gradle to 5.1

build.gradle

@@ -1,4 +1,5 @@
 plugins {
+  // usage: gradle dependencyUpdates -Drevision=release
   id "com.github.ben-manes.versions" version "0.20.0"
 }
 
@@ -61,6 +62,6 @@ subprojects {
 	}
 }
 
-task wrapper(type: Wrapper) {
-	gradleVersion = '4.10.2'
+wrapper() {
+	gradleVersion = '5.1'
 }