Remove superfluos 'Too many connections' test

The scenario where MariaDB 10.1.21 sends an error packet as the first
packet is covered by a test in mysql_protocol_tests, using similated
traffic.

test/mysql_tests.erl

@@ -56,42 +56,6 @@ failing_connect_test() ->
     end,
     process_flag(trap_exit, false).
 
-too_many_connections_test_() ->
-    {timeout, 30, fun too_many_connections/0}.
-
-too_many_connections() ->
-    process_flag(trap_exit, true),
-    try
-        Pids = too_many_connections(200),
-        %?debugFmt("Max connections seems to be ~p~n", [length(Pids)]),
-        %% Collect all the trapped exits.
-        receive {'EXIT', _, Reason} ->
-            ?assertMatch({1040, <<"08004">>, <<"Too many connections">>},
-                         Reason)
-        after 50 -> ok
-        end,
-        lists:foreach(fun (Pid) ->
-                              exit(Pid, normal),
-                              receive {'EXIT', _, normal} -> ok
-                              after 50 -> ok
-                              end
-                      end,
-                      Pids)
-    after
-        process_flag(trap_exit, false),
-        timer:sleep(1000)
-    end.
-
-too_many_connections(Max) when Max > 0 ->
-    Options = [{user, ?user}, {password, ?password}, {connect_timeout, 10000}],
-    case mysql:start_link(Options) of
-        {ok, Pid} ->
-            [Pid | too_many_connections(Max - 1)];
-        {error, E} ->
-            ?assertMatch({1040, <<"08004">>, <<"Too many connections">>}, E),
-            []
-    end.
-
 successful_connect_test() ->
     %% A connection with a registered name and execute initial queries and
     %% create prepared statements.