ci: Stop testing on CentOS 7

Let's stop actively testing on CentOS 7 from this point on. The latest
stable version v2019.2 will be the last fully supported release on this
platform. We may backport patches there if needed.

This will allow us to shed a lot of legacy and dual-paths code that
rendered the code more complex. It'll also reduce friction on new
initiatives like unified core by default and sysusers.

Closes: #1785
Approved by: cgwalters

.papr.yml

@@ -69,42 +69,6 @@ artifacts:
 
 ---
 
-inherit: true
-
-context: c7-primary
-
-required: true
-
-cluster:
-  hosts:
-    - name: vmcheck1
-      distro: centos/7/atomic/smoketested
-    - name: vmcheck2
-      distro: centos/7/atomic/smoketested
-    - name: vmcheck3
-      distro: centos/7/atomic/smoketested
-  container:
-    image: registry.centos.org/centos/centos:7
-
-# We only want the sanitizers on Fedora
-env:
-    HOSTS: vmcheck1 vmcheck2 vmcheck3
-    CFLAGS: ''
-
-extra-repos:
-  - name: atomic-centos-continuous
-    baseurl: https://ci.centos.org/artifacts/sig-atomic/rdgo/centos-continuous/build
-    gpgcheck: 0
-
-tests:
-  # we're still on devmapper here; we need to expand rootfs for tests
-  - for vm in vmcheck{1..3}; do ssh $vm lvresize -r -L +5G atomicos/root; done
-  - ci/vmcheck-provision.sh
-  - ci/build-check.sh
-  - make vmcheck
-
----
-
 branches:
   - master
   - auto