Apply resurfacing update changes

Removed mentions of an upcoming change to the sort parameter to ps.concat() that has been implemented (v 1.0.0)

Removed mentions of pd.DataFrame.append() which has been deprecated in 1.4.0 <https://pandas.pydata.org/docs/whatsnew/v1.4.0.html#whatsnew-140-deprecations-frame-series-append>

Author: martin-martin