Added PayPal requriement

composer.json

@@ -20,6 +20,7 @@
     "magento/module-backend": "100.0.*",
     "magento/module-directory": "100.0.*",
     "magento/module-theme": "100.0.*",
+    "magento/module-paypal": "100.0.*",
     "magento/framework": "100.0.*",
     "magento/magento-composer-installer": "*",
     "adyen/php-api-library": "*"

etc/module.xml

@@ -29,6 +29,7 @@
             <module name="Magento_Sales"/>
             <module name="Magento_Quote"/>
             <module name="Magento_Checkout"/>
+            <module name="Magento_Paypal"/>
         </sequence>
     </module>
 </config>
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