Remove all margins from those cells.
Rather add margins to their respective subviews:
- ScrollableExpressionView
- ScrollableExactApproximateExpressionsView.
As a notable consequence, the distance in HistoryViewCell between its
subviews becomes 10 instead of 5.
In passing, replace
- Metric::HistoryHorizontalMargin = 10
- ScrollableExactApproximateExpressionsView::k_digitHorizontalMargin = 10
- HistoryViewCell::k_digitVerticalMargin = 5
- ScrollableExactApproximateExpressionsCell::k_margin = 5
by
- Metric::CommonSmallMargin = 5
- Metric::CommonLargeMargin = 10.
