Remove incorrect documentation in aptpkg.purge

Fixes #15529
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error
Fix sphinx build error