refactor: is_probably_private_reply: Remove reaction-specific code

Instead, look up the 1:1 chat in `receive_imf::add_parts()`. This is a more generic approach to fix
assigning outgoing reactions to 1:1 chats in the multi-device setup. Although currently both
approaches give the same result, this way we can even implement a "react privately"
functionality. Maybe it sounds useless, but it seems better to have less reaction-specific code.

src/receive_imf.rs

@@ -1077,6 +1077,12 @@ async fn add_parts(
                     chat_id_blocked = chat.blocked;
                 }
             }
+            if chat_id.is_none() && is_dc_message == MessengerMessage::Yes {
+                if let Some(chat) = ChatIdBlocked::lookup_by_contact(context, to_id).await? {
+                    chat_id = Some(chat.id);
+                    chat_id_blocked = chat.blocked;
+                }
+            }
 
             // automatically unblock chat when the user sends a message
             if chat_id_blocked != Blocked::Not {
@@ -1722,11 +1728,6 @@ async fn is_probably_private_reply(
         }
     }
 
-    let is_reaction = mime_parser.parts.iter().any(|part| part.is_reaction);
-    if is_reaction {
-        return Ok(false);
-    }
-
     Ok(true)
 }