build: remove JCenter repository (#1438)

https://jfrog.com/blog/into-the-sunset-bintray-jcenter-gocenter-and-chartcenter/

Author: valfirst

build.gradle

@@ -13,7 +13,6 @@ plugins {
 }
 
 repositories {
-    jcenter()
     mavenCentral()
 }