Enable clippy::filter_map_identity (#8741)

This PR enables the
[`clippy::filter_map_identity`](https://rust-lang.github.io/rust-clippy/master/index.html#/filter_map_identity)
rule and fixes the outstanding violations.

Release Notes:

- N/A

crates/recent_projects/src/recent_projects.rs

@@ -325,10 +325,7 @@ impl PickerDelegate for RecentProjectsDelegate {
             .unzip();
 
         let highlighted_match = HighlightedMatchWithPaths {
-            match_label: HighlightedText::join(
-                match_labels.into_iter().filter_map(|name| name),
-                ", ",
-            ),
+            match_label: HighlightedText::join(match_labels.into_iter().flatten(), ", "),
             paths: if self.render_paths { paths } else { Vec::new() },
         };
         Some(