Deprecate redundant render_app_async_stream_with_context

[alexisfontaine]

I was inspecting the internals of the leptos_axum crate and noticed duplicate code in the logic for handling the async stream.
Furthermore, render_app_async_stream_with_context and render_app_async_with_context appear to have identical behavior. I looked for potential differences, but found none.

I propose to deprecate render_app_async_with_context in favor of render_app_async_stream_with_context, which is also exposed in the Actix integration.

[gbj]

Thanks for pointing this out. I will tag this as 0.9 and simply remove the duplicate — marking something deprecated is not technically a breaking change but can be effectively break CI if people are linting, so it's easiest to deprecate in a minor release or simply remove, especially for something that's not likely to be widely used like this.