Trim ORDER BY/DISTINCT aggregate pathkeys in gather_grouping_paths
Similar to d8a295389, trim off any PathKeys which are for ORDER BY /
DISTINCT aggregate functions from the PathKey List for the Gather Merge
paths created by gather_grouping_paths(). These additional PathKeys are
not valid to use
Trim ORDER BY/DISTINCT aggregate pathkeys in gather_grouping_paths
Similar to d8a295389, trim off any PathKeys which are for ORDER BY /
DISTINCT aggregate functions from the PathKey List for the Gather Merge
paths created by gather_grouping_paths(). These additional PathKeys are
not valid to use
