fix(dialyzer): remote the extra str/1

apps/emqx_connector/src/emqx_connector_mqtt.erl

@@ -179,11 +179,4 @@ basic_config(#{
     }.
 
 clientid(Id) ->
-    list_to_binary(lists:concat([str(Id), ":", node()])).
-
-str(A) when is_atom(A) ->
-    atom_to_list(A);
-str(B) when is_binary(B) ->
-    binary_to_list(B);
-str(S) when is_list(S) ->
-    S.
+    list_to_binary(lists:concat([Id, ":", node()])).