Change zuul tenant ansible version to 8

This also removes the unecessary pins in the other tenants.

Change-Id: Id06b6b34868a276726f1a14447c752551066d882

zuul/main.yaml

@@ -17,7 +17,6 @@
       - local-admin
       - infra-root
       - tenant-group
-    default-ansible-version: '6'
     max-nodes-per-job: 10
     source:
       gerrit:
@@ -86,7 +85,6 @@
 - tenant:
     name: nebulous
     admin-rules: *admin_rules
-    default-ansible-version: '6'
     max-nodes-per-job: 10
     source:
       gerrit:
@@ -123,7 +121,6 @@
 - tenant:
     name: openstack
     admin-rules: *admin_rules
-    default-ansible-version: '6'
     max-nodes-per-job: 10
     source:
       gerrit:
@@ -1531,7 +1528,6 @@
 - tenant:
     name: vexxhost
     admin-rules: *admin_rules
-    default-ansible-version: '6'
     max-nodes-per-job: 10
     source:
       gerrit:
@@ -1632,7 +1628,7 @@
 - tenant:
     name: zuul
     admin-rules: *admin_rules
-    default-ansible-version: '6'
+    default-ansible-version: '8'
     max-nodes-per-job: 10
     source:
       gerrit:
@@ -1709,7 +1705,6 @@
 - tenant:
     name: pyca
     admin-rules: *admin_rules
-    default-ansible-version: '6'
     max-nodes-per-job: 1
     source:
       gerrit:
@@ -1736,7 +1731,6 @@
 - tenant:
     name: pypa
     admin-rules: *admin_rules
-    default-ansible-version: '6'
     max-nodes-per-job: 1
     source:
       gerrit: