keymap: Fix shift- modifier symbol (#25238)

Closes #25230

```
The shift- modifier can only be used in combination with a letter to indicate the uppercase version. For example shift-g matches typing G. Although on many keyboards shift is used to type punctuation characters like (, the keypress is not considered to be modified and so shift-( does not match.
```

[Document](https://zed.dev/docs/key-bindings#keybinding-syntax)

Release Notes:

- Fixed Keymap use `shift-` modifier symbol

assets/keymaps/default-linux.json

@@ -343,9 +343,9 @@
       "alt-ctrl-f12": "editor::GoToTypeDefinitionSplit",
       "alt-shift-f12": "editor::FindAllReferences",
       "ctrl-m": "editor::MoveToEnclosingBracket",
-      "ctrl-shift-\\": "editor::MoveToEnclosingBracket",
-      "ctrl-shift-[": "editor::Fold",
-      "ctrl-shift-]": "editor::UnfoldLines",
+      "ctrl-|": "editor::MoveToEnclosingBracket",
+      "ctrl-{": "editor::Fold",
+      "ctrl-}": "editor::UnfoldLines",
       "ctrl-k ctrl-l": "editor::ToggleFold",
       "ctrl-k ctrl-[": "editor::FoldRecursive",
       "ctrl-k ctrl-]": "editor::UnfoldRecursive",