Fix compilation buck of ktfmt idea plugin after PR 502

Summary:
[This PR](#502) converted the code to Kotlin, but we forgot to adapt our internal buck compilation to it and as a result things are failing.

```
BUILD FAILED
File not found: `fbsource//xplat/ktfmt/ktfmt_idea_plugin/src/main/java/com/facebook/ktfmt/intellij/Notifications.java`
```

Reviewed By: cortinico

Differential Revision: D61208006

fbshipit-source-id: c90f8de7920ab86cda279b07daf7a59b7777a8c2

ktfmt_idea_plugin/src/main/kotlin/com/facebook/ktfmt/intellij/KtfmtConfigurable.kt

@@ -49,7 +49,7 @@ class KtfmtConfigurable(project: Project) :
     }
 
     row {
-      comboBox(UiFormatterStyle.entries.toList())
+      comboBox(UiFormatterStyle.values().toList())
           .label("Code style:")
           .bindItem(
               getter = { settings.uiFormatterStyle },