Enable clippy::useless_format (#8758)

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

Release Notes:

- N/A

crates/collab_ui/src/channel_view.rs

@@ -376,7 +376,7 @@ impl Item for ChannelView {
                 (_, false) => format!("#{} (disconnected)", channel.name),
             }
         } else {
-            format!("channel notes (disconnected)")
+            "channel notes (disconnected)".to_string()
         };
         Label::new(label)
             .color(if selected {

crates/collab_ui/src/chat_panel/message_editor.rs

@@ -137,9 +137,9 @@ impl MessageEditor {
     ) {
         self.editor.update(cx, |editor, cx| {
             if let Some(channel_name) = channel_name {
-                editor.set_placeholder_text(format!("Message #{}", channel_name), cx);
+                editor.set_placeholder_text(format!("Message #{channel_name}"), cx);
             } else {
-                editor.set_placeholder_text(format!("Message Channel"), cx);
+                editor.set_placeholder_text("Message Channel", cx);
             }
         });
         self.channel_id = Some(channel_id);

crates/collab_ui/src/collab_panel.rs

@@ -952,7 +952,7 @@ impl CollabPanel {
                         })
                         .ok();
                 }))
-                .tooltip(move |cx| Tooltip::text(format!("Open shared screen"), cx))
+                .tooltip(move |cx| Tooltip::text("Open shared screen", cx))
             })
     }
 
@@ -2220,7 +2220,7 @@ impl CollabPanel {
                 });
 
                 if let Some(name) = channel_name {
-                    SharedString::from(format!("{}", name))
+                    SharedString::from(name.to_string())
                 } else {
                     SharedString::from("Current Call")
                 }

crates/collab_ui/src/notification_panel.rs

@@ -778,7 +778,7 @@ fn format_timestamp(
             "just now".to_string()
         }
     } else if date.next_day() == Some(today) {
-        format!("yesterday")
+        "yesterday".to_string()
     } else {
         format!("{:02}/{}/{}", date.month() as u32, date.day(), date.year())
     }