Remove flaky test case

This test has proved its point and now just exists to randomly fail some
builds depending on race conditions with the garbage collector.

test/jiffy_14_bignum_memory_leak.erl

@@ -1,29 +0,0 @@
-% This file is part of Jiffy released under the MIT license.
-% See the LICENSE file for more information.
-
--module(jiffy_14_bignum_memory_leak).
-
--include_lib("eunit/include/eunit.hrl").
-
-
-bignum_encoding_leak_test_() ->
-    run_gc(),
-    Before = erlang:memory(binary),
-    encode_bignums(1000000),
-    run_gc(),
-    After = erlang:memory(binary),
-    ?_assert(After - Before < 100000).
-
-
-run_gc() ->
-    [erlang:garbage_collect(Pid) || Pid <- erlang:processes()].
-
-
-encode_bignums(N) ->
-    {_, Ref} = spawn_monitor(fun() ->
-        [jiffy:encode(1072502107250210725021072502) || _ <- lists:seq(1, N)]
-    end),
-    receive
-        {'DOWN', Ref, process, _, _} ->
-            ok
-    end.