Use our omemo sid/fingerprint in qr code

Current clients sid/fingerprint will be shown in following format:
`xmpp:<user@server>?omemo-sid-<numerical-sid>=<omemo-fingerprint-hex-string>`

Fix https://github.com/profanity-im/profanity/issues/1320

tests/unittests/omemo/stub_omemo.c

@@ -120,3 +120,9 @@ omemo_device_id()
 {
     return 123;
 }
+
+char*
+omemo_qrcode_str()
+{
+    return NULL;
+}