Update sample inventory to inventory v2

The key "nodes" was deprecated in favor of "targets" in later versions
of Bolt 1.x, and obsoleted/replaced in Bolt 2.x. Updating docs to be
current, valid inventory file sytnax.

Author: reidmv

Diff for: documentation/provision.md

@@ -53,15 +53,15 @@ Example inventory.yaml Bolt inventory file:
 ```yaml
 ---
 groups:
-  - name: pe_nodes
+  - name: puppet-enterprise-nodes
     config:
       transport: ssh
       ssh:
         host-key-check: false
         user: centos
         run-as: root
         tty: true
-    nodes:
+    targets:
       - pe-xl-core-0.lab1.puppet.vm
       - pe-xl-core-1.lab1.puppet.vm
       - pe-xl-core-2.lab1.puppet.vm