Line numbers in "MPS model Viewer" should be aligned like "Side-by-side viewer"

[mgronover]

The current situation is that line numbers are hidden by the Actions placed on the same panel:

• The small red rectangle shows the wrong location of the line numbers within the panel.
• The larger red rectange shows the wrong alignment of the line numbers belonging to the right editor component.

The line numbers should be placed and aligned like in the "Side-by-side viewer".

[mgronover]

Fixed with https://github.com/JetBrains/MPS-extensions/pull/673