Prune 2.7.1

Fixes a real Deep Clean false positive: a game could show up as
cleanable on a machine that never had it installed.

Fixed

• A game/launcher rule (Steam, Epic Games Launcher, Riot Client,
  League of Legends) could report itself as cleanable even when that
  program was never installed. These 8 rules only ever checked whether
  a folder existed, not whether the program itself was actually
  installed -- and a launcher can create its own placeholder folders for
  titles it merely lists, not titles you've installed. They're now
  cross-checked against the same real, registry-based installed-programs
  list that already powers the Applications screen, so a rule can no
  longer claim a game is here when it isn't.