fix(browse): theme change with no state refresh

* cards.reset() is no longer needed
* onCleared is no longer needed：
  * It's called when the theme changes, and we didn't actually
want this, as we wanted to persist the rows in the ViewModel

AnkiDroid/src/main/java/com/ichi2/anki/CardBrowser.kt

@@ -557,7 +557,6 @@ open class CardBrowser :
         super.onCollectionLoaded(col)
         Timber.d("onCollectionLoaded()")
         registerReceiver()
-        cards.reset()
 
         window.setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN)
         deckSpinnerSelection.apply {

AnkiDroid/src/main/java/com/ichi2/anki/browser/CardBrowserViewModel.kt

@@ -675,18 +675,6 @@ class CardBrowserViewModel(
 
     fun getRowAtPosition(position: Int) = cards[position]
 
-    override fun onCleared() {
-        super.onCleared()
-        invalidate()
-    }
-
-    private fun invalidate() {
-        Timber.d("invalidate")
-        // TODO: this may no longer be needed now we call invalidate from onCleared
-        cards.clear()
-        selectNone()
-    }
-
     private suspend fun updateSavedSearches(func: MutableMap<String, String>.() -> Unit): Map<String, String> {
         val filters = savedSearches().toMutableMap()
         func(filters)