[human] address comments from PR

Author: bigH

test/mcp/server/transports/streamable_http_transport_test.rb

@@ -689,7 +689,7 @@ class StreamableHTTPTransportTest < ActiveSupport::TestCase
 
           response = stateless_transport.handle_request(request)
           assert_equal 202, response[0]
-          assert_equal({ "Content-Type" => "application/json" }, response[1])
+          assert_empty(response[1])
 
           body = response[2][0]
           assert_nil(body)