Remove unnecessary repositories{} block from top level build.gradle (#35644)

Summary:
Pull Request resolved: #35644

The `repositories{}` block in the top level build.gradle is not needed anymore
The React Native Gradle Plugin is taking care of it.
Users can still specify if they need to provide custom repositories.

Changelog:
[Android] [Changed] - Remove unnecessary repositories{} block from top level build.gradle

Reviewed By: cipolleschi

Differential Revision: D42033953

fbshipit-source-id: 8ec1c12147fae68302ab47c60045869c72d1812c

Author: cortinico

template/android/build.gradle

@@ -19,19 +19,3 @@ buildscript {
         classpath("com.facebook.react:react-native-gradle-plugin")
     }
 }
-
-allprojects {
-    repositories {
-        maven {
-            // All of React Native (JS, Obj-C sources, Android binaries) is installed from npm
-            url("$rootDir/../node_modules/react-native/android")
-        }
-        maven {
-            // Android JSC is installed from npm
-            url("$rootDir/../node_modules/jsc-android/dist")
-        }
-        mavenCentral()
-        google()
-        maven { url 'https://www.jitpack.io' }
-    }
-}