Migrate DeckPickerTest to kotlin

[lukstbit]

Purpose / Description

Migrate DeckPickerTest.java to kotlin following the migration guide.

How Has This Been Tested?

Ran the tests.

Checklist

• You have not changed whitespace unnecessarily (it makes diffs hard to read)
• You have a descriptive commit message with a short title (first line, max 50 chars).
• Your code follows the style of the project (e.g. never omit braces in if statements)
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[david-allison]

Looks great! A couple of imports were removed

[mikehardy]

Thanks!