Fix mysql execute test after disconnect.

Previously it used to be ActiveRecord::Result, now it seems to be an array

Author: JesseChavez

test/db/mysql/simple_test.rb

@@ -451,10 +451,10 @@ def test_execute_after_disconnect
 
     # active record change of behaviour 7.1, reconnects on query execution.
     result = assert_nothing_raised do
-      connection.execute('SELECT 1 + 2')
+      connection.execute('SELECT 1 + 2 as total')
     end
 
-    assert_equal 3, result.rows.flatten.first
+    assert_equal 3, result.first['total']
   ensure
     connection.reconnect!
   end