Enable clippy::useless_conversion (#8767)

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

Release Notes:

- N/A

crates/workspace/src/dock.rs

@@ -221,7 +221,7 @@ impl Dock {
                     return;
                 };
                 if panel.is_zoomed(cx) {
-                    workspace.zoomed = Some(panel.to_any().downgrade().into());
+                    workspace.zoomed = Some(panel.to_any().downgrade());
                     workspace.zoomed_position = Some(position);
                 } else {
                     workspace.zoomed = None;

crates/workspace/src/pane.rs

@@ -899,7 +899,7 @@ impl Pane {
             if not_shown_files == 1 {
                 file_names.push(".. 1 file not shown".into());
             } else {
-                file_names.push(format!(".. {} files not shown", not_shown_files).into());
+                file_names.push(format!(".. {} files not shown", not_shown_files));
             }
         }
         (

crates/workspace/src/workspace.rs

@@ -2961,7 +2961,7 @@ impl Workspace {
         })?;
 
         let Some(id) = view.id.clone() else {
-            return Err(anyhow!("no id for view")).into();
+            return Err(anyhow!("no id for view"));
         };
         let id = ViewId::from_proto(id)?;
 
@@ -3744,7 +3744,7 @@ fn open_items(
 
         let tasks = tasks.collect::<Vec<_>>();
 
-        let tasks = futures::future::join_all(tasks.into_iter());
+        let tasks = futures::future::join_all(tasks);
         for (ix, path_open_result) in tasks.await.into_iter().flatten() {
             opened_items[ix] = Some(path_open_result);
         }