Honor default_mode in NormalBefore (#29518)

Addresses
[this](https://github.com/zed-industries/zed/pull/28103#issuecomment-2832038415)
comment.

Release Notes:

- Improved default helix keybindings

crates/vim/src/insert.rs

@@ -36,7 +36,7 @@ impl Vim {
                     });
                 });
             });
-            self.switch_mode(Mode::Normal, false, window, cx);
+            self.switch_mode(self.default_mode(cx), false, window, cx);
             return;
         }