gtk4: Recalculate Borders menu entry
gtk4-client has "Recalculate Borders" menu entry as commented out gtk3 code, never implemented to gtk4. Implement it, or drop completely if there's no use for it.
gtk4-client has "Recalculate Borders" menu entry as commented out gtk3 code, never implemented to gtk4. Implement it, or drop completely if there's no use for it.