replace jcenter() with mavenCentral()

Jcenter is being shutdown so migrating to Maven Central.

Author: jkasten2

android/build.gradle

@@ -4,7 +4,7 @@ version '3.2.7'
 buildscript {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 
     dependencies {
@@ -15,7 +15,7 @@ buildscript {
 rootProject.allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }
 

example/android/build.gradle

@@ -1,7 +1,7 @@
 buildscript {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 
     dependencies {
@@ -12,7 +12,7 @@ buildscript {
 allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }