Do not specify a Kotlin version in the RN rootProject (#33589)

Summary:
As we introduced KGP inside `ReactAndroid` (cc ShikaSD), we now need to specify a version for it (as users will consume that build on Android New Architecture.

Currently, the version is loaded in the RN `rootProject` which is not available on user's project. I'm cleaning this up.

## Changelog

[Internal] - Do not specify a Kotlin version in the RN rootProject

Pull Request resolved: https://github.com/facebook/react-native/pull/33589

Test Plan:
Tested on a nightly version with

```
npx react-native init RNNightly --version nightly
```

Reviewed By: mdvacca

Differential Revision: D35476777

Pulled By: cortinico

fbshipit-source-id: 5a819ef5fa9a6886d7b7b683f31d59cb05a49f29

ReactAndroid/build.gradle

@@ -8,7 +8,7 @@
 plugins {
     id("com.android.library")
     id("com.facebook.react")
-    id("org.jetbrains.kotlin.android")
+    id("org.jetbrains.kotlin.android") version "1.6.10"
     id("maven-publish")
     id("de.undercouch.download")
 }