Fix `cmd-c` not copying text inside macOS notebook cell editors.

Previously, the macOS notebook keymap bound `cmd-c` to
`notebook::InterruptKernel` in notebook contexts, including
`NotebookEditor > Editor`. This shadowed the normal editor copy shortcut
while editing notebook cells.


## Solution

Move the macOS notebook interrupt shortcut from `cmd-c` to `ctrl-c`.

This keeps the notebook interrupt shortcut available while allowing the
normal editor keybindings to handle:

- `cmd-c` for copy
- `cmd-x` for cut
- `cmd-v` for paste

inside notebook cell editors.
- This change is macOS-specific.

Release Notes:

- N/A

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Co-authored-by: dino <dinojoaocosta@gmail.com>