Remove not needed initialization in chatwin_new()

00dbc1ba7c attempted to fix
https://github.com/profanity-im/profanity/issues/1449.

Here we revert the part about initializing is_omemo in chatwin_new()
since this is done in win_create_chat() already.

The actual mistake was the wrong cast of the muc window which is fixed
by the same commit. The mistake was introduced in in 3370418d71.

While being at it we also remove the is_ox initialization since this is
handled in win_create_chat()/win_create_muc() too.

src/ui/chatwin.c

@@ -80,7 +80,6 @@ chatwin_new(const char* const barejid)
         }
     }
 
-    chatwin->is_omemo = FALSE;
 #ifdef HAVE_OMEMO
     if (omemo_automatic_start(barejid)) {
         omemo_start_session(barejid);
@@ -92,9 +91,6 @@ chatwin_new(const char* const barejid)
         iq_mam_request(chatwin);
     }
 
-    // XEP-0373: OpenPGP for XMPP
-    chatwin->is_ox = FALSE;
-
     return chatwin;
 }