Improve XEP-0308 compliance

Disallow correcting historical MUC messages, as the XEP-308 requires.

Previous changes introduce problem with
"Illicit LMC attempt from conference@server/user for message from user"

During investigation it was revealed that XEP does not recommend support
of historical MUC messages correction.

```
When used in a Multi-User Chat (XEP-0045) context,
corrections must not be allowed (by the receiver)
for messages received before the sender joined the room -
particularly a full JID leaving the room
then rejoining and correcting a message SHOULD be disallowed,
as the entity behind the full JID in the MUC may have changed.
```
https://xmpp.org/extensions/xep-0308.html#rules

XEP details mentioned by @jubalh
Bug discovered and solution improved by  @jaeckel

src/xmpp/message.c

@@ -1101,14 +1101,6 @@ _handle_groupchat(xmpp_stanza_t* const stanza)
         }
     }
 
-    xmpp_stanza_t* replace_id_stanza = xmpp_stanza_get_child_by_ns(stanza, STANZA_NS_LAST_MESSAGE_CORRECTION);
-    if (replace_id_stanza) {
-        const char* replace_id = xmpp_stanza_get_id(replace_id_stanza);
-        if (replace_id) {
-            message->replace_id = strdup(replace_id);
-        }
-    }
-
     message->body = xmpp_message_get_body(stanza);
 
     // check omemo encryption
@@ -1153,6 +1145,14 @@ _handle_groupchat(xmpp_stanza_t* const stanza)
     if (is_muc_history) {
         sv_ev_room_history(message);
     } else {
+        // XEP-0308 states: `corrections must not be allowed (by the receiver) for messages received before the sender joined the room`
+        xmpp_stanza_t* replace_id_stanza = xmpp_stanza_get_child_by_ns(stanza, STANZA_NS_LAST_MESSAGE_CORRECTION);
+        if (replace_id_stanza) {
+            const char* replace_id = xmpp_stanza_get_id(replace_id_stanza);
+            if (replace_id) {
+                message->replace_id = strdup(replace_id);
+            }
+        }
         sv_ev_room_message(message);
     }