Update gradle version and buildToolsVersion in Launcher3 build.gradle file.

Test: Gradle build of Launcher3 completed successully in Android Studio
3.2.1

Change-Id: If53639985613cde15a125b58e2c527ff864277ea
diff --git a/build.gradle b/build.gradle
index b59f264..1b9df53 100644
--- a/build.gradle
+++ b/build.gradle
@@ -4,7 +4,7 @@
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.2.0-rc03'
+        classpath 'com.android.tools.build:gradle:3.2.1'
         classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.6'
     }
 }
@@ -16,7 +16,7 @@
 
 android {
     compileSdkVersion 28
-    buildToolsVersion '28.0.2'
+    buildToolsVersion '28.0.3'
 
     defaultConfig {
         minSdkVersion 21