.gitlab-ci.yml: Do not build Samba for Ubuntu 16.04 or Debian 9 any longer

These only have Python 3.5 and we want to increase the minimum to Python 3.6.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>

bootstrap/config.py

@@ -374,14 +374,6 @@ end
 
 
 DEB_DISTS = {
-    'debian9': {
-        'docker_image': 'debian:9',
-        'vagrant_box': 'debian/stretch64',
-        'replace': {
-            'language-pack-en': '',   # included in locales
-            'liburing-dev': '',   # not available
-        }
-    },
     'debian10': {
         'docker_image': 'debian:10',
         'vagrant_box': 'debian/buster64',
@@ -390,17 +382,6 @@ DEB_DISTS = {
             'liburing-dev': '',   # not available
         }
     },
-    'ubuntu1604': {
-        'docker_image': 'ubuntu:16.04',
-        'vagrant_box': 'ubuntu/xenial64',
-        'replace': {
-            'python-gpg': 'python-gpgme',
-            'python3-gpg': 'python3-gpgme',
-            'glusterfs-common': '',
-            'libcephfs-dev': '',
-            'liburing-dev': '',   # not available
-        }
-    },
     'ubuntu1804': {
         'docker_image': 'ubuntu:18.04',
         'vagrant_box': 'ubuntu/bionic64',