Fixed the error in nutanix sample install-config.yaml by moving the username, and password feilds under the prismCental stanza

Author: waljaber

modules/installation-nutanix-config-yaml.adoc

@@ -64,8 +64,8 @@ platform:
       endpoint:
         address: your.prismcentral.domainname <1>
         port: 9440 <1>
-    password: samplepassword <1>
-    username: sampleadmin <1>
+      password: samplepassword <1>
+      username: sampleadmin <1>
     prismElements:
     - endpoint:
         address: your.prismelement.domainname