Mark ACS specific sections in Troubleshooting guide for Campaign Push Notifications

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Which topic?

https://developer.adobe.com/client-sdks/documentation/troubleshooting-guides/push-notifications/

### What's wrong with the content?

In section _Set up a server key_ the steps starting _Verify that Firebase server key is configured in the Campaign instance (Android)_ and starting _Verify that the APNS server certificate is configured in the Campaign instance (iOS)_ are specific to Campaign Standard.
Likewise in [Set up an Android or iOS app to receive push notifications](https://developer.adobe.com/client-sdks/documentation/troubleshooting-guides/push-notifications/#set-up-an-android-or-ios-app-to-receive-push-notifications)

### What changes do you propose?

1. Mark those steps as specific to Campaign Standard
2. Provide steps for Campaign Classic

### Anything else that can help to cover this?

_No response_

Start with the linked push-notifications troubleshooting guide and inspect the “Set up a server key” and “Set up an Android or iOS app to receive push notifications” sections. Mark the identified steps as Campaign Standard-specific and add the corresponding Campaign Classic steps, then verify both sections clearly distinguish the two Campaign products.

Written by the indexing model from the issue text.