The removed rules are the following: fillSpacingFromBoardEdge, minFillSpacingFromBoardEdge, maxFillSpacingFromBoardEdge, spacing, minSpacing, maxSpacing, spacingTop, minSpacingTop, maxSpacingTop, spacingLeft, minSpacingLeft, maxSpacingLeft, spacingBottom, minSpacingBottom, maxSpacingBottom, spacingRight, minSpacingRight, maxSpacingRight

The replacement for them is the new keepOut rule. More info about it is available here.

The spacing rule was used to control the margins for auto positioning: to achieve the same result, now you can apply a keepOut rule to an element node

The spacing rule was also used to control the margin from traces/pads/vias to fills: to change that distance now you can use the keepOut rule, using a keepout towards a net

The effect of the fillSpacingFromBoardEdge rule can be achieved with the keepOut rule as well: either by applying a keepOut from the GND net to the layout, or from the layout to a net.