Preserve text when toggling view once.

Fixes an issue, where the written text would be lost if a user toggled view
once in the `AddMessageDialogFragment`. This is unexpected, as when toggling
view once from the `MediaReviewFragment` the previously written text is
preserved.

app/src/main/java/org/thoughtcrime/securesms/mediasend/v2/review/AddMessageDialogFragment.kt

@@ -101,6 +101,7 @@ class AddMessageDialogFragment : KeyboardEntryDialogFragment(R.layout.v2_media_a
     binding.hud.setOnClickListener { dismissAllowingStateLoss() }
 
     binding.content.viewOnceToggle.setOnClickListener {
+      dismissAllowingStateLoss()
       viewModel.incrementViewOnceState()
     }