AppDomain documentation misleading

### Type of issue

Code doesn't work

### Description

This page starts with a large block of code that demonstrates AppDomains, then some remarks. However, the code provided does not work with .NET Core. This note does explain it, but it's half a page below the example code, and in a purple "Note" box rather than a red "Caution" box, like the far less important note below. Essentially, the page gives incorrect information then an unclear note that effectively says "disregard everything else on this page". I spent some time trying to get the example code to work before reading the note.

### Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.appdomain?view=net-8.0

### Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System/AppDomain.xml

### Document Version Independent Id

eae62dad-109f-0239-95c1-2777c3117163

### Article author

@dotnet-bot