Bug#1123542: lintian: warn that autopkgtest skip-not-installable is deprecated

[Graham Inggs <ginggs@debian.org>]

Source: lintian
Version: 2.127.0
Severity: wishlist

Dear Lintian Maintainers

Please add a warning that the autopkgtest restriction
'skip-not-installable' is now deprecated.  The README [1] of
autopkgtest contains the following text:

skip-not-installable (deprecated):
This restriction may cause a test to miss a regression due to
installability issues. If one wants to skip certain architectures, use
the Architecture field for that.

I think checking in debian/test/control for
   Restrictions:.*skip-not-installable
might be all that's needed.

Regards
Graham


[1] https://salsa.debian.org/ci-team/autopkgtest/-/blob/master/doc/README.package-tests.rst