Fix for CONPY-221:

Removed __del__ method from cursors.py to prevent
raisiing if cursor was already properly closed via close()
method.

testing/test/integration/test_cursor.py

@@ -637,7 +637,6 @@ class TestCursor(unittest.TestCase):
     def test_closed(self):
         cursor = self.connection.cursor()
         cursor.close()
-        cursor.close()
         self.assertEqual(cursor.closed, True)
         try:
             cursor.execute("set @a:=1")
@@ -1420,6 +1419,19 @@ class TestCursor(unittest.TestCase):
         del cursor
         del conn
 
+    def test_conpy221(self):
+        conn = create_connection()
+        cursor = conn.cursor()
+        cursor.close()
+        del cursor
+
+        cursor = conn.cursor()
+        del cursor
+        try:
+            cursor.close()   # noqa: F821
+        except Exception:
+            pass
+
     def test_conpy91(self):
         with create_connection() as connection:
             with connection.cursor() as cursor: