replace ruby 3.4 preview1 with preview2 (#127)

* replace ruby 3.4 preview1 with preview2

* fix spec

* remarks

.github/workflows/ci.yml

@@ -22,7 +22,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby:
-          - '3.4.0-preview1'
+          - '3.4.0-preview2'
           - '3.3'
           - '3.2'
           - '3.1'

spec/rdkafka/consumer/topic_partition_list_spec.rb

@@ -114,12 +114,18 @@
   end
 
   describe "#to_s" do
+    let(:expected) do
+      if RUBY_VERSION >= '3.4.0'
+        "<TopicPartitionList: {\"topic1\" => [<Partition 0>, <Partition 1>]}>"
+      else
+        "<TopicPartitionList: {\"topic1\"=>[<Partition 0>, <Partition 1>]}>"
+      end
+    end
+
     it "should return a human readable representation" do
       list = Rdkafka::Consumer::TopicPartitionList.new
       list.add_topic("topic1", [0, 1])
 
-      expected = "<TopicPartitionList: {\"topic1\"=>[<Partition 0>, <Partition 1>]}>"
-
       expect(list.to_s).to eq expected
     end
   end