remove unnecessary react native gradle plugin apply (#37)

Author: CHOIMINSEOK

android/app/build.gradle

@@ -10,10 +10,6 @@ def isNewArchitectureEnabled() {
 
 def IS_NEW_ARCHITECTURE_ENABLED = isNewArchitectureEnabled()
 
-if (IS_NEW_ARCHITECTURE_ENABLED) {
-    apply plugin: "com.facebook.react"
-}
-
 def DEFAULT_COMPILE_SDK_VERSION = 26
 def DEFAULT_BUILD_TOOLS_VERSION = "26.0.3"
 def DEFAULT_TARGET_SDK_VERSION = 26