Add dependency mention

Author: mnocon

docs/commerce/payment/enable_paypal_payments.md

@@ -9,7 +9,7 @@ By using Payum to integrate PayPal into your application, you can offer your cus
 
 Before you can proceed with integrating PayPal, you must [create a PayPal business account](https://www.paypal.com/bizsignup/#/singlePageSignup) and obtain API credentials.
 
-Install the PayPal package:
+Install the PayPal package and the required dependencies:
 
 ```bash
 composer require payum/paypal-express-checkout-nvp php-http/guzzle7-adapter php-http/message php-http/message-factory

docs/commerce/payment/enable_stripe_payments.md

@@ -10,7 +10,7 @@ By using Payum to integrate Stripe into your application, you can securely proce
 
 Before you can proceed with integrating Stripe, [sign up for a Stripe account](https://dashboard.stripe.com/register) and obtain the API keys required for integration.
 
-Install the Stripe package:
+Install the PayPal package and the required dependencies:
 
 ```bash
 composer require payum/stripe php-http/guzzle7-adapter php-http/message php-http/message-factory
@@ -44,4 +44,4 @@ ibexa:
             strp_checkout:
                 name: "Translated Stripe Checkout name"
 
-```
+```