gpui: Update docs to reflect removal of View, ViewContext, WindowContext (#24008)

This PR updates function signatures, docstrings, and gpui's other
documentation to reflect it's new state following the merge of `Model`
and `View` into `Entity` as well as the removal of `WindowContext`.

Release Notes:

- N/A

crates/gpui/src/window/prompts.rs

@@ -68,7 +68,7 @@ pub struct RenderablePromptHandle {
     pub(crate) view: Box<dyn PromptViewHandle>,
 }
 
-/// Use this function in conjunction with [AppContext::set_prompt_renderer] to force
+/// Use this function in conjunction with [App::set_prompt_builder] to force
 /// GPUI to always use the fallback prompt renderer.
 pub fn fallback_prompt_renderer(
     level: PromptLevel,