Update all_practices (#496)
Update all_practices (#496)

Remove reference to mean
annapowellsmith/openpresc,ebmdatalab/openprescribing,ebmdatalab/openprescribing,ebmdatalab/openprescribing,annapowellsmith/openpresc,annapowellsmith/openpresc,ebmdatalab/openprescribing,annapowellsmith/openpresc