MC-31168: [2.3.x] Mark core payment methods as deprecated in Admin

Author: svitja

app/code/Magento/Paypal/etc/adminhtml/system.xml

@@ -38,7 +38,7 @@
             </group>
             <group id="deprecated_payment_methods" translate="label" sortOrder="5" showInDefault="1" showInWebsite="1" showInStore="1">
                 <label>Deprecated Payment Methods:</label>
-                <comment><![CDATA[<b>Note:</b> These payment methods have been deprecated because they are no longer compliant. We recommend that these payment method to be disabled to prevent new orders, since the payment processor might not support them. Please migrate to the official payment methods extensions from Magento Marketplace instead and disable deprecated payment integrations as soon as possible.]]></comment>
+                <comment><![CDATA[These payment methods have been deprecated because they are no longer compliant. We recommend that these payment method to be disabled to prevent new orders, since the payment processor might not support them. Please migrate to the official payment methods extensions from Magento Marketplace instead and disable deprecated payment integrations as soon as possible.]]></comment>
                 <attribute type="expanded">1</attribute>
                 <fieldset_css>paypal-top-section payments-other-header deprecated-message</fieldset_css>
                 <frontend_model>\Magento\Config\Block\System\Config\Form\Fieldset</frontend_model>

app/design/adminhtml/Magento/backend/Magento_Config/web/css/source/_module.less

@@ -150,11 +150,6 @@
 }
 
 .deprecated-message > .comment {
-    background: @deprecated__light_color;
-    border: 1px solid @deprecated__dark_color;
-    border-radius: 3px;
-    color: @deprecated__dark_color;
-    margin: 5px 0 0;
-    padding: 3px 7px;
-    position: relative;
+    &:extend(.message all);
+    &:extend(.message-notice all);
 }

lib/web/css/source/lib/variables/_colors.less

@@ -120,6 +120,3 @@
 
 @active__color: @theme__color__secondary;
 @error__color: @color-red10;
-
-@deprecated__light_color: #faecec;
-@deprecated__dark_color: #d6474a;