Focus notebook cell container correctly

[msujew]

What it does

When using the "Jupyter Keymap" plugin, pressing B should trigger the notebook.cell.insertCodeCellBelowAndFocusContainer command. However, this command should not focus the newly inserted cell.

This change adjusts the behavior of the command to ensure that B can be pressed repeatedly to create new cells.

How to test

1. Install the Jupyter Keymap plugin (comes with the Jupyter plugin)
2. Open a notebook and focus a cell (but not the editor within)
3. Press B to create a new cells below the current cell (or A to create one above)
4. Ensure that the focus doesn't go to the text editor.
5. Ensure that pressing the keybinding multiple times correctly creates a new cell each time.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[jonah-iden]

Loogs good 👍