Render man/man5/puppetconf.5 correctly

Previously, `rake genmanpages` generated warnings when converting ronn to man:

    roff: ./man/man5/puppetconf.5
    warn: unrecognized block tag: "hr"
    warn: unexpected text: "Return a YAML hash with up to three keys:"

The first warning was because definition lists need to have a space between each
item. As a result the entire line "Return a YAML hash with up to three keys" was
omitted from the output.

The second warning was because '* * *' is not valid in ronn.

lib/puppet/defaults.rb

@@ -2126,10 +2126,12 @@ def self.initialize_default_settings!(settings)
           can produce node information. The command must:
 
           * Take the name of a node as a command-line argument.
+
           * Return a YAML hash with up to three keys:
             * `classes` --- A list of classes, as an array or hash.
             * `environment` --- A string.
             * `parameters` --- A list of top-scope variables to set, as a hash.
+
           * For unknown nodes, exit with a non-zero exit code.
 
           Generally, an ENC script makes requests to an external data source.

lib/puppet/reference/configuration.rb

@@ -95,6 +95,5 @@
 
   [confguide]: https://puppet.com/docs/puppet/latest/config_about_settings.html
 
-  * * *
 
 EOT

man/man5/puppet.conf.5

@@ -689,6 +689,7 @@ This setting\'s value must be the path to an executable command that can produce
 Take the name of a node as a command\-line argument\.
 .
 .IP "\(bu" 4
+Return a YAML hash with up to three keys:
 .
 .IP "\(bu" 4
 \fBclasses\fR \-\-\- A list of classes, as an array or hash\.