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/project/src/worktree.rs

@@ -1866,7 +1866,7 @@ impl Snapshot {
         })
     }
 
-    /// Update the `git_status` of the given entries such that files'
+    /// Updates the `git_status` of the given entries such that files'
     /// statuses bubble up to their ancestor directories.
     pub fn propagate_git_statuses(&self, result: &mut [Entry]) {
         let mut cursor = self