bump Android Gradle Plugin to 3.4.2 (#25652)

Summary:
Bump Android Gradle Plugin to 3.4.2, includes bug fixes and improvements

## Changelog

[Android][Changed] - bump Android Gradle Plugin to 3.4.2
Pull Request resolved: https://github.com/facebook/react-native/pull/25652

Test Plan: RNTester builds and runs as expected

Differential Revision: D16258865

Pulled By: mdvacca

fbshipit-source-id: c20600e3c7fc44793f42a0061bbb22a6ead9f0e4

build.gradle.kts

@@ -10,7 +10,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath("com.android.tools.build:gradle:3.4.1")
+        classpath("com.android.tools.build:gradle:3.4.2")
         classpath("de.undercouch:gradle-download-task:3.4.3")
 
         // NOTE: Do not place your application dependencies here; they belong

template/android/build.gradle

@@ -13,7 +13,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath("com.android.tools.build:gradle:3.4.1")
+        classpath("com.android.tools.build:gradle:3.4.2")
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files