You're using calculated shipping which is setting the shipping amounts based on packages such as padded envelopes and boxes. Those rates also include tracking.
If you want to send the stickers in a regular envelope, you shouldn't be using the calculated shipping option. Use the ''I'll enter fixed prices manually'' option and enter your own shipping amount.
Be aware tho that sending something with no tracking could cause problems, such as the buyer can claim they did not receive their order. Without tracking you cannot prove that you actually mailed it. Also, using a regular letter envelope like one you'd mail a b'day card in doesn't offer much protection against damage, if that's what you intend to use.
