tests: fix badarg on close of resource

The resource was closed by t_hdr_close/1 and end_per_group/1, resulting
in a badarg:

    hdr_histogram_SUITE:end_per_group failed
    Reason: badarg

Author: msantos

test/hdr_histogram_SUITE.erl

@@ -97,10 +97,6 @@ init_per_group(_GroupName, Config) ->
     [{raw,Raw},{cor,Cor}|Config].
 
 end_per_group(_GroupName, Config) ->
-    Raw = ?config(raw,Config),
-    Cor = ?config(cor,Config),
-    hdr_histogram:close(Raw),
-    hdr_histogram:close(Cor),
     Config.
 
 init_per_testcase(_TestCase, Config) ->