Cleanups preparing for WindowContext refactor (#22475)

* Remove unnecessary WindowContext and ViewContext '_ lifetimes

* Removed some cases where WindowContext has a different name than `cx`.

Release Notes:

- N/A

crates/gpui/src/app.rs

@@ -1490,7 +1490,7 @@ impl Context for AppContext {
 
     fn update_window<T, F>(&mut self, handle: AnyWindowHandle, update: F) -> Result<T>
     where
-        F: FnOnce(AnyView, &mut WindowContext<'_>) -> T,
+        F: FnOnce(AnyView, &mut WindowContext) -> T,
     {
         self.update(|cx| {
             let mut window = cx