inline_completion_button: Replace UserStore with CloudUserStore (#35456)

This PR replaces usages of the `UserStore` in the inline completion
button with the `CloudUserStore`.

Release Notes:

- N/A

crates/zed/src/zed.rs

@@ -336,7 +336,7 @@ pub fn initialize_workspace(
         let edit_prediction_button = cx.new(|cx| {
             inline_completion_button::InlineCompletionButton::new(
                 app_state.fs.clone(),
-                app_state.user_store.clone(),
+                app_state.cloud_user_store.clone(),
                 inline_completion_menu_handle.clone(),
                 cx,
             )