Fix broken string_ext_test due to change in timezone

- Russian time was changed to UTC+3 from UTC+4 recently. This broke the
  string_to_ext test.

activesupport/test/core_ext/string_ext_test.rb

@@ -321,7 +321,7 @@ def test_partial_string_to_time
       now = Time.now
       assert_equal Time.local(now.year, now.month, now.day, 23, 50), "23:50".to_time
       assert_equal Time.utc(now.year, now.month, now.day, 23, 50), "23:50".to_time(:utc)
-      assert_equal Time.local(now.year, now.month, now.day, 18, 50), "13:50 -0100".to_time
+      assert_equal Time.local(now.year, now.month, now.day, 17, 50), "13:50 -0100".to_time
       assert_equal Time.utc(now.year, now.month, now.day, 23, 50), "22:50 -0100".to_time(:utc)
     end
   end