Warning messages are styled with the info message type

The edit and view modes for the annotation have a message as a fallback for when the annotation cannot be found. This message is an info message. Seeing how we do things now, I'd have expected this message to be a warning or an error instead.

See https://github.com/xwiki/xwiki-platform/blob/d11ca5d781f8a42a85bc98eb82306c1431e764d4/xwiki-platform-core/xwiki-platform-annotation/xwiki-platform-annotation-ui/src/main/resources/AnnotationCode/Macros.xml#L121

This was found and reported when looking for a solution to XWIKI-22433.