Upgrade to Gradle 6.0.1 to prevent pushing .sha256 and .sha512 to Nexus

Secure checksums can be pushed if systemProp.org.gradle.internal.publish.checksums.insecure
is removed from gradle.porperties

See https://issues.apache.org/jira/browse/INFRA-14923
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 9f08c4c..c571965 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -15,7 +15,7 @@
 
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionSha256Sum=a1eb4439c0a85bc7e64a22658d862e43b7d0ddfbf69a7abf6256e0b7514295df
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.0-all.zip
+distributionSha256Sum=6f6cfdbb12a577c3845522a1c7fbfe1295ea05d87edabedd4e23fd2bf02b88b1
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.0.1-all.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists