update severity assertion to support more freetds versions

Severity level changed with this commit in freetds FreeTDS/freetds@6642360. Since the severity check isn't essential we allow for either severity in order to support a wider range of freetds versions.

Author: bvogelzang

test/client_test.rb

@@ -146,7 +146,7 @@ class ClientTest < TinyTds::TestCase
         action = lambda { client.execute('SELECT 1 as [one]').each }
         assert_raise_tinytds_error(action) do |e|
           assert_equal 20047, e.db_error_number
-          assert_equal 9, e.severity
+          assert_includes [1,9], e.severity
           assert_match %r{dead or not enabled}i, e.message, 'ignore if non-english test run'
         end
         close_client(client)