remove deprecated queue_explicit_gc_run_operation_threshold config

Author: Ayanda-D

deps/rabbit/BUILD.bazel

@@ -116,9 +116,6 @@ _APP_ENV = """[
 	    {cluster_nodes, {[], disc}},
 
 	    {config_entry_decoder, [{passphrase, undefined}]},
-
-	    %% rabbitmq-server#973
-	    {queue_explicit_gc_run_operation_threshold, 1000},
 	    {background_gc_enabled, false},
 	    {background_gc_target_interval, 60000},
 	    %% rabbitmq-server#589

deps/rabbit/Makefile

@@ -99,9 +99,6 @@ define PROJECT_ENV
 	    {cluster_nodes, {[], disc}},
 
 	    {config_entry_decoder, [{passphrase, undefined}]},
-
-	    %% rabbitmq-server#973
-	    {queue_explicit_gc_run_operation_threshold, 1000},
 	    {background_gc_enabled, false},
 	    {background_gc_target_interval, 60000},
 	    %% rabbitmq-server#589

deps/rabbit/test/backing_queue_SUITE.erl

@@ -193,18 +193,12 @@ end_per_group1(_, Config) ->
 
 init_per_testcase(Testcase, Config) when Testcase == variable_queue_requeue;
                                          Testcase == variable_queue_fold ->
-    ok = rabbit_ct_broker_helpers:rpc(
-           Config, 0, application, set_env,
-           [rabbit, queue_explicit_gc_run_operation_threshold, 0]),
     rabbit_ct_helpers:testcase_started(Config, Testcase);
 init_per_testcase(Testcase, Config) ->
     rabbit_ct_helpers:testcase_started(Config, Testcase).
 
 end_per_testcase(Testcase, Config) when Testcase == variable_queue_requeue;
                                         Testcase == variable_queue_fold ->
-    ok = rabbit_ct_broker_helpers:rpc(
-           Config, 0, application, set_env,
-           [rabbit, queue_explicit_gc_run_operation_threshold, 1000]),
     rabbit_ct_helpers:testcase_finished(Config, Testcase);
 end_per_testcase(Testcase, Config) ->
     rabbit_ct_helpers:testcase_finished(Config, Testcase).