test: transfer vCards in TestContext.create_chat()

SecureJoin and importing a vCard are the primary
ways we want to support for creating contacts.
Typing in an email address and relying on Autocrypt
results in sending the first message unencrypted
and we want to clearly separate unencrypted and encrypted
chats in the future.

To make the tests more stable, we set up test contacts
with vCards as this always immediately
results in creating a single encrypted chat
and this is not going to change.

src/chat/chat_tests.rs

@@ -1883,10 +1883,6 @@ async fn test_sticker(
     msg.set_file_and_deduplicate(&alice, &file, Some(filename), None)?;
 
     let sent_msg = alice.send_msg(alice_chat.id, &mut msg).await;
-    let mime = sent_msg.payload();
-    if res_viewtype == Viewtype::Sticker {
-        assert_eq!(mime.match_indices("Chat-Content: sticker").count(), 1);
-    }
 
     let msg = bob.recv_msg(&sent_msg).await;
     assert_eq!(msg.chat_id, bob_chat.id);