Older version of kotlin

[xmartgithub]

FAILURE: Build failed with an exception.

• What went wrong: A problem occurred configuring project ':flutter_opentok'.

  The Android Gradle plugin supports only Kotlin Gradle plugin version 1.3.10 and higher. The following dependencies do not satisfy the required version: project ':flutter_opentok' -> org.jetbrains.kotlin:kotlin-gradle-plugin:1.2.71