Make slash commands more discoverable (#12480)

<img width="648" alt="image"
src="https://github.com/zed-industries/zed/assets/482957/a63df904-fbbe-4e0a-80b2-c98ebee90690">

Release Notes:

- N/A

Co-authored-by: Nathan <nathan@zed.dev>

crates/assistant/src/slash_command/active_command.rs

@@ -19,8 +19,8 @@ impl SlashCommand for ActiveSlashCommand {
         "insert active tab".into()
     }
 
-    fn tooltip_text(&self) -> String {
-        "insert active tab".into()
+    fn menu_text(&self) -> String {
+        "Insert Active Tab".into()
     }
 
     fn complete_argument(