Remove hard dependency on Kotlin

[eleftherias]

Closes gh-9811

[eleftherias]

As of Kotlin 1.4, the Kotlin plugin adds the stdlib dependency by default.
In order to prevent that dependency from being added automatically (since it is optional in Spring Security) we can set kotlin.stdlib.default.dependency to false.
https://kotlinlang.org/docs/gradle.html#dependency-on-the-standard-library