Bump gradle from 4.2.0 to 4.2.1 (#2325)

Summary:
Bumps gradle from 4.2.0 to 4.2.1.

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Pull Request resolved: https://github.com/facebook/flipper/pull/2325

Reviewed By: priteshrnandgaonkar

Differential Revision: D28474742

Pulled By: mweststrate

fbshipit-source-id: fa58186520441ea86ae7204e63843a028c3b53e8

build.gradle

@@ -11,7 +11,7 @@ buildscript {
         mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.2.0'
+        classpath 'com.android.tools.build:gradle:4.2.1'
         classpath 'com.vanniktech:gradle-maven-publish-plugin:0.15.1'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$KOTLIN_VERSION"
         classpath "org.jetbrains.dokka:dokka-gradle-plugin:1.4.32"