TELCODOCS-1837: Fix erroneous example in day 1 bare metal networking config

There is no "nmstate" key under "networkConfig" inside the
install-config, as can be observed from all of the other examples. (The
"nmstate" key is where the NMState data lives in the Secret generated
from the install-config to associate with the BareMetalHost, or by the
user when adding nodes on Day 2.)

modules/ipi-install-configuring-host-network-interfaces-for-subnets.adoc

@@ -35,22 +35,21 @@ networking:
 [source,yaml]
 ----
 networkConfig:
-  nmstate:
-    interfaces:
-    - name: <interface_name> <1>
-      type: ethernet
-      state: up
-      ipv4:
-        enabled: true
-        dhcp: false
-        address:
-        - ip: <node_ip> <2>
-          prefix-length: 24
-        gateway: <gateway_ip> <3>
-        dns-resolver:
-          config:
-            server:
-            - <dns_ip> <4>
+  interfaces:
+  - name: <interface_name> <1>
+    type: ethernet
+    state: up
+    ipv4:
+      enabled: true
+      dhcp: false
+      address:
+      - ip: <node_ip> <2>
+        prefix-length: 24
+      gateway: <gateway_ip> <3>
+      dns-resolver:
+        config:
+          server:
+          - <dns_ip> <4>
 ----
 +
 <1> Replace `<interface_name>` with the interface name.