add back buildToolsVersion to build.gradle (#23316)

Summary:
add back buildToolsVersion to build.gradle, because many third-party modules depend on it. The lack of this info causing issues in 0.58.

[Android] [Changed] - add back buildToolsVersion to template
Pull Request resolved: https://github.com/facebook/react-native/pull/23316

Differential Revision: D13974264

Pulled By: hramos

fbshipit-source-id: 058fc5617196d6481d1b69d2420c8b2be9cf4f81

template/android/build.gradle

@@ -2,6 +2,7 @@
 
 buildscript {
     ext {
+        buildToolsVersion = "28.0.3"
         minSdkVersion = 16
         compileSdkVersion = 28
         targetSdkVersion = 27