Hide labels in Drop Down Menu

First, thanks for this amazing plugin. He helped me a lot.

I have a Woo site, and I would like to delegate operations to a ShopManager. How can I hide options from a drop-down list (Product Type).

I thank you in advance.

Example : hide the first option below :

<label for="product-type">
	<select id="product-type" name="product-type">
		<optgroup label="Type de produit">
			<option value="variable-subscription">Abonnement Variable</option>
			<option value="wsspg_subscription">Wsspg Subscription Product</option>
		</optgroup>
	</select>
</label>