Remove debian-jessie nodesets

We don't have any jobs using these, so we can remove them.

Change-Id: I6c00b5cefa5f141426da8edb56163205c884ee25
Depends-On: https://review.openstack.org/563673
Depends-On: https://review.openstack.org/563682
Depends-On: https://review.openstack.org/564016
Depends-On: https://review.openstack.org/564019
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

zuul.d/nodesets.yaml

@@ -5,12 +5,6 @@
       - name: centos-7
         label: centos-7
 
-- nodeset:
-    name: debian-jessie
-    nodes:
-      - name: debian-jessie
-        label: debian-jessie
-
 - nodeset:
     name: debian-stable
     nodes:
@@ -143,12 +137,6 @@
       - name: primary
         label: centos-7
 
-- nodeset:
-    name: legacy-debian-jessie
-    nodes:
-      - name: primary
-        label: debian-jessie
-
 # TODO(pabelanger): Remove once project-config is update to run fedora-27.
 - nodeset:
     name: legacy-fedora-26