fixed spec exist for mcp_sdk related specs

Author: patvice

spec/ruby_llm/mcp/adapters/mcp_sdk_sse_spec.rb

@@ -40,7 +40,9 @@ def client
   end
 
   after(:all) do # rubocop:disable RSpec/BeforeAfterAll
-    MCPSdkSSERunner.instance.stop
+    if RUBY_VERSION >= "3.2.0"
+      MCPSdkSSERunner.instance.stop
+    end
   end
 
   describe "connection" do

spec/ruby_llm/mcp/adapters/mcp_sdk_stdio_spec.rb

@@ -40,7 +40,9 @@ def client
   end
 
   after(:all) do # rubocop:disable RSpec/BeforeAfterAll
-    MCPSdkStdioRunner.instance.stop
+    if RUBY_VERSION >= "3.2.0"
+      MCPSdkStdioRunner.instance.stop
+    end
   end
 
   describe "connection" do

spec/ruby_llm/mcp/adapters/mcp_sdk_streamable_spec.rb

@@ -39,7 +39,9 @@ def client
   end
 
   after(:all) do # rubocop:disable RSpec/BeforeAfterAll
-    MCPSdkStreamableRunner.instance.stop
+    if RUBY_VERSION >= "3.2.0"
+      MCPSdkStreamableRunner.instance.stop
+    end
   end
 
   describe "connection" do