Update tenses of doc comment summary lines (#4161)

This PR updates the tenses used by the summary line of doc comments to
match the [Rust API documentation
conventions](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#summary-sentence).

Specifically:

> The summary line should be written in third person singular present
indicative form. Basically, this means write ‘Returns’ instead of
‘Return’.

I'm sure there are plenty occurrences that I missed.

Release Notes:

- N/A

crates/gpui/src/view.rs

@@ -64,7 +64,7 @@ impl<V: 'static> View<V> {
         Entity::downgrade(self)
     }
 
-    /// Update the view's state with the given function, which is passed a mutable reference and a context.
+    /// Updates the view's state with the given function, which is passed a mutable reference and a context.
     pub fn update<C, R>(
         &self,
         cx: &mut C,
@@ -156,7 +156,7 @@ impl<V: 'static> WeakView<V> {
         Entity::upgrade_from(self)
     }
 
-    /// Update this view's state if it hasn't been released.
+    /// Updates this view's state if it hasn't been released.
     /// Returns an error if this view has been released.
     pub fn update<C, R>(
         &self,