Include note about 204 in hx-delete docs and examples

[alexpetros]

Description

This issue has come up in the Discord a few times, as well as on GitHub: #1130

In part because Mozilla suggets a 204 - NO CONTENT status code as an idiomatic response to the DELETE HTTP method, a lot of people come to HTMX (myself included) expecting that returning a 204 will remove the element that sent the delete request from the DOM.

The reason HTMX does not do this is because of an HTMX-wide policy that the 204 response essentially means "do not swap", which is perfectly reasonable once you get to know how the library works. It's also, however, a recurring stumbling block for new users.

I think this can be easily rectified by linking people to the appropriate part of the documentation from the relevant delete pages—since it is reasonably likely they will find the hx-delete or delete row examples before digging into the mildly more obscure section about response codes. It also highlights the increased relevance of status codes in HTMX design patterns, relative to JSON-based patterns.