Build: Replace kotlin android extensions with parcelize for wordpress

Since this lib utilizes the '@parcelize' annotation (ie.
'SelectedDateProvider' on 'StatsActivity'), the
'kotlin-android-extensions' plugin cannot be removed completely, but
instead it needs to be replaced with the 'kotlin-parcelize' plugin.

Author: ParaskP7

WordPress/build.gradle

@@ -51,7 +51,7 @@ repositories {
 
 apply plugin: 'com.android.application'
 apply plugin: 'kotlin-android'
-apply plugin: 'kotlin-android-extensions'
+apply plugin: 'kotlin-parcelize'
 apply plugin: 'se.bjurr.violations.violation-comments-to-github-gradle-plugin'
 apply plugin: 'kotlin-allopen'
 apply plugin: 'kotlin-kapt'
@@ -235,11 +235,6 @@ android {
     }
 }
 
-// allows us to use cool things like @Parcelize annotations
-androidExtensions {
-    experimental = true
-}
-
 dependencies {
     implementation project(path: ':mp4compose')
     implementation project(path:':libs:stories-android:stories')