Fix code bugs and add cert trust step in grant-identity page

- Fix RemovePackageAsync: package.Id.FamilyName -> package.Id.FullName
  (FamilyName causes runtime deployment errors; FullName is correct)
- Fix DeprovisionPackageForAllUsersAsync: same FamilyName -> FullName fix
- Fix per-machine PowerShell unregister command: add missing closing quote
- Rewrite contradictory MinVersion bullets as clear either/or choice
- Add IMPORTANT callout: self-signed cert must be added to Trusted People
  store before Add-AppxPackage will accept it (most common first-time failure)

Fixes ADO #568632

Co-authored-by: Copilot <[email protected]>

Author: GrantMeStrength