Make a single re-usable banner component (#27412)

Release Notes:

- Fixed an issue where both the predict edit and git onboarding banners
would both show at the same time.

crates/zeta/src/init.rs

@@ -43,8 +43,6 @@ pub fn init(cx: &mut App) {
                         .edit_prediction_provider = Some(EditPredictionProvider::None)
                 },
             );
-
-            crate::onboarding_banner::clear_dismissed(cx);
         });
     })
     .detach();