Adjust async level of tests

test/consumer_offset_fetcher_test.exs

@@ -1,5 +1,5 @@
 defmodule KafkaexLagExporter.ConsumerOffsetFetcher.Test do
-  use ExUnit.Case, async: true
+  use ExUnit.Case
   use Patch
 
   @test_consumer_group_name1 "test_consumer_1"

test/topic_name_parser_test.exs

@@ -1,6 +1,5 @@
 defmodule KafkaexLagExporterTopicNameParserTest do
-  use ExUnit.Case
-  doctest KafkaexLagExporter.TopicNameParser
+  use ExUnit.Case, async: true
 
   test "should parse single topic" do
     test_member_assignment =