fix: Fix crash when receiving a verification-gossiping message which a contact also sends to itself (#7032)

This should fix https://github.com/chatmail/core/issues/7030; @r10s if
you could test whether it fixes your problem

The crash happened if you received a message that has the from contact
also in the "To: " and "Chat-Group-Member-Fpr: " headers. Not sure how
it happened that such a message was created.

src/receive_imf.rs

@@ -3642,7 +3642,7 @@ async fn mark_recipients_as_verified(
         return Ok(());
     }
     for to_id in to_ids.iter().filter_map(|&x| x) {
-        if to_id == ContactId::SELF {
+        if to_id == ContactId::SELF || to_id == from_id {
             continue;
         }