fix(wallet): use proper isDm check for wallet button visibility

The wallet button should only appear in genuine DM rooms. The previous
logic (isDm || activeMembersCount == 2L) was overly broad as it would
show the wallet in any 2-person room, including private rooms that
are not direct messages.

Now uses only roomInfo.isDm which properly checks:
- isDirect flag is true (Matrix spec DM indicator)
- activeMembersCount <= 2 (at most 2 active members)

This ensures the wallet button only appears in real 1:1 DM rooms.

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/MessagesPresenter.kt

@@ -295,7 +295,7 @@ class MessagesPresenter(
             dmUserVerificationState = dmUserVerificationState,
             roomMemberModerationState = roomMemberModerationState,
             topBarSharedHistoryIcon = topBarSharedHistoryIcon,
-            isDmRoom = roomInfo.isDm || roomInfo.activeMembersCount == 2L,
+            isDmRoom = roomInfo.isDm,
             successorRoom = roomInfo.successorRoom,
             eventSink = ::handleEvent,
         )