update Gradle wrapper -> 6.9.3

./gradlew wrapper --gradle-version 6.9.3

- update wrapper properties
- update wrapper JAR
- update wrapper scripts

ref:

- https://docs.gradle.org/current/userguide/gradle_wrapper.html#sec:upgrading_wrapper
- https://gradle.org/releases/

Author: Christopher J. Brody

gradle/wrapper/gradle-wrapper.jar

@@ -1,6 +1,5 @@
-#Mon Sep 21 10:18:41 CDT 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.9.3-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https://services.gradle.org/distributions/gradle-6.7.1-all.zip