Override InputMethodSwitcherDialog theme for watch

On watches, the default color palette is dark. This overrides the theme
used for the IME Switcher menu to ensure the correct dark color palette
is used on watch.

Flag: android.view.inputmethod.ime_switcher_revamp
Bug: 311791923
Test: flash on watch; adb shell input keyevent KEYCODE_SYM; observe
Change-Id: Ie870bc8e6a6b4819a9e604984586b8b47ef22738