Remove remark that Adblock Edge uses less memory than Adblock Plus

It's not true. Ablock Edge is an (apparently unmaintained) fork for an
older version of Adblock Plus. Apart from the rebranding, the only
change is the removal of the acceptable ads option.
Merge pull request #302 from fhd/abp-memory

Remove remark that Adblock Edge uses less memory than Adblock Plus