Remove workspaceLoaded setting

The `workspaceLoaded` notification setting was originally designed to
control the display of a popup message that said:

  "workspace loaded, {} rust packages"

This popup was removed and replaced by a much sleeker message in the
VSCode status bar that provides a real-time status while loading:

  rust-analyzer: {}/{} packages

This was done as part of #3587

The new status-bar indicator is unobtrusive and shouldn't need to be
disabled.  So this setting is removed.

crates/rust-analyzer/src/main_loop.rs

@@ -415,8 +415,7 @@ fn loop_turn(
         });
     }
 
-    let show_progress =
-        !loop_state.workspace_loaded && world_state.config.notifications.workspace_loaded;
+    let show_progress = !loop_state.workspace_loaded;
 
     if !loop_state.workspace_loaded
         && loop_state.roots_scanned == loop_state.roots_total