test(banned): attempt to fix flaky test

Example failure:
https://github.com/emqx/emqx/actions/runs/4821105856/jobs/8587006829#step:8:4495

```
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
emqx_common_test_helpers:wait_for_down failed on line 434
Reason: {{t_session_taken,178,timeout},[{emqx_common_test_helpers,...},{...}|...]}
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Testing lib.emqx.emqx_banned_SUITE: *** FAILED test case 4 of 5 ***
%%% emqx_banned_SUITE ==> t_session_taken: FAILED
%%% emqx_banned_SUITE ==> {{t_session_taken,178,timeout},
 [{emqx_common_test_helpers,wait_for_down,6,
                            [{file,"/__w/emqx/emqx/source/apps/emqx/test/emqx_common_test_helpers.erl"},
                             {line,434}]},
  {emqx_banned_SUITE,t_session_taken,1,
                     [{file,"/__w/emqx/emqx/source/apps/emqx/test/emqx_banned_SUITE.erl"},
                      {line,176}]},
  {test_server,ts_tc,3,[{file,"test_server.erl"},{line,1782}]},
  {test_server,run_test_case_eval1,6,[{file,"test_server.erl"},{line,1291}]},
  {test_server,run_test_case_eval,9,[{file,"test_server.erl"},{line,1223}]}]}
```

apps/emqx/test/emqx_banned_SUITE.erl

@@ -186,7 +186,7 @@ t_session_taken(_) ->
                     false
             end
         end,
-        6000
+        15_000
     ),
     Publish(),
 

apps/emqx_resource/src/emqx_resource.app.src

@@ -1,7 +1,7 @@
 %% -*- mode: erlang -*-
 {application, emqx_resource, [
     {description, "Manager for all external resources"},
-    {vsn, "0.1.14"},
+    {vsn, "0.1.15"},
     {registered, []},
     {mod, {emqx_resource_app, []}},
     {applications, [