Learn keys dialog: Too large margin

[egmontkob]

Is there an existing issue for this?

• I have searched the existing issues

Midnight Commander version and build configuration

4.8.33, git

Operating system

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Is this issue reproducible using the latest version of Midnight Commander?

• I confirm the issue is still reproducible with the latest version of Midnight Commander

How to reproduce

Our dialog boxes typically have 1 empty character column inside the border.

"Learn keys" having 2-3 on the left and 5-7 on the right not only looks unpleasant, but could also be used for better purposes (c.f. #5038).

Expected behavior

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Actual behavior

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Additional context

No response