Updating kotlin plugin location

[missingcharacter]

Checklist

• Provide a short description and link to your plugin.

• Make sure you CI tests for your plugin and they are green.

  If you are using github, you might want to use the
  `plugin_test` action from [asdf-actions](https://github.com/asdf-vm/actions)
  

• asdf-plugins CI sanity checks are green on your PullRequest.

  You can test locally using:
  
  ```bash
  $ git checkout patch-1
  $ ./test_plugin.sh --file plugins/kotlin
  Checking plugins/kotlin
  OK plugins/kotlin
  ```
  

Other Information

I'm just changing the location of the plugin

[smorimoto]

Could you rebase this?

[smorimoto]

Thanks @missingcharacter!