Fix tests usage of to_s for Ruby 3.4 and later

Aparently Hash#to_s formatting changed with Ruby 3.4 so we need to track
that now.

test/test_Stl_Map.cpp

@@ -5,6 +5,7 @@
 #include "embed_ruby.hpp"
 #include <rice/rice.hpp>
 #include <rice/stl.hpp>
+#include <ruby/version.h>
 
 using namespace Rice;
 
@@ -257,7 +258,11 @@ TESTCASE(Iterate)
   ASSERT_EQUAL(3u, result.size());
 
   std::string result_string = result.to_s().str();
+#if RUBY_API_VERSION_MAJOR == 3 && RUBY_API_VERSION_MINOR >= 4
+  ASSERT_EQUAL("{\"five\" => 10, \"seven\" => 14, \"six\" => 12}", result_string);
+#else
   ASSERT_EQUAL("{\"five\"=>10, \"seven\"=>14, \"six\"=>12}", result_string);
+#endif
 }
 
 TESTCASE(ToEnum)
@@ -280,7 +285,12 @@ TESTCASE(ToEnum)
   ASSERT_EQUAL(3u, result.size());
 
   std::string result_string = result.to_s().str();
+
+#if RUBY_API_VERSION_MAJOR == 3 && RUBY_API_VERSION_MINOR >= 4
+  ASSERT_EQUAL("{\"five\" => 10, \"seven\" => 14, \"six\" => 12}", result_string);
+#else
   ASSERT_EQUAL("{\"five\"=>10, \"seven\"=>14, \"six\"=>12}", result_string);
+#endif
 }
 
 TESTCASE(ToEnumSize)