build: remove jcenter from /example

Author: iBotPeaches

example/android/build.gradle

@@ -2,7 +2,6 @@
 
 buildscript {
     repositories {
-        jcenter()
         google()
     }
     dependencies {
@@ -16,7 +15,6 @@ buildscript {
 allprojects {
     repositories {
         mavenLocal()
-        jcenter()
         google()
         maven {
             // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm