amcheck for PG11 in Debian

Hi Peter,

if I understood it correctly, amcheck in Debian (and on
apt.postgresql.org) is a backpatch of the PG11+ functionality,
for older versions.

As we just switched to PG11 in Debian, it no longer makes sense to
keep the package there, so we should get it removed. Is that correct?

(Of course the package will stay on apt.postgresql.org as long as PG10
is supported there.)

Christoph