Update links to manual

etc/adminhtml/system/adyen_getting_started.xml

@@ -28,7 +28,7 @@
         <frontend_model>Magento\Config\Block\System\Config\Form\Fieldset</frontend_model>
         <comment><![CDATA[
                             <ul class="adyen-list">
-                                <li><a target="_blank" href="https://docs.adyen.com/manuals/magento2-integration">Manual for setting up the module</a></li>
+                                <li><a target="_blank" href="https://docs.adyen.com/manuals/magento/magento2-integration">Manual for setting up the module</a></li>
                                 <li><a target="_blank" href="https://www.adyen.com/home/payment-services/plug-ins/magento#form"><strong>Sign</strong> up for a test account</a></li>
                                 <li>The latest version of the <a target="_blank" href="https://github.com/adyen/adyen-magento2/releases">Adyen Magento module is also available through GitHub</a>.</li>
                             </ul>

etc/adminhtml/system/adyen_required_settings.xml

@@ -30,7 +30,7 @@
             <label>Merchant Account</label>
             <config_path>payment/adyen_abstract/merchant_account</config_path>
             <tooltip><![CDATA[The merchant account identifier you want to process the (transaction) request with. Find this at the top of the screen in the Adyen Customer Area, where you will see [YourCompanyAccount] > [YourMerchantAccount] . Please note that the merchant account is different from the company account; a company account can have one or more merchant accounts.]]></tooltip>
-            <comment><![CDATA[<a target="_blank" href="https://docs.adyen.com/manuals/magento2-integration/settings-in-the-customer-area">Click here for explanation.</a>]]></comment>
+            <comment><![CDATA[<a target="_blank" href="https://docs.adyen.com/manuals/magento/magento2-integration/settings-in-the-customer-area">Click here for explanation.</a>]]></comment>
         </field>
         <field id="demo_mode" translate="label" type="select" sortOrder="20" showInDefault="1" showInWebsite="1" showInStore="1">
             <label>Test/Production Mode</label>