Remove shortcode 'code' (#19035)

A long time ago, we added a new shortcode `codenew` as a replacement of
the `code` shortcode. The intention was to consolidate all example
manifests to a single subdirectory, i.e. `content/<lang>/examples`. Now
this transition is almost over. We have only two instances where the old
`code` shortcode is referenced.

This PR makes the `policy.rego` file inlined content so that all
referenes to `code` are killed. We can safely drop the `code` shortcode.
If desired, we can rename the `codenew` shortcode to `code` in a
(series of) separate PR(s).

layouts/shortcodes/code.html

@@ -1,38 +0,0 @@
-{{ $p := .Page }}
-{{ $file := .Get "file" }}
-{{ $codelang := .Get "language" | default (path.Ext $file | strings.TrimPrefix ".") }} 
-{{ $fileDir := path.Split $file }}
-{{ $bundlePath := path.Join .Page.File.Dir $fileDir.Dir }}
-{{ $filename := path.Join $p.File.Dir $file }}
-{{ $ghlink := printf "https://%s/blob/master/content/%s/%s" site.Params.githubwebsiterepo .Page.Lang $filename | safeURL }}
-{{/* First assume this is a bundle and the file is inside it. */}}
-{{ $resource := $p.Resources.GetMatch (printf "%s*" $file ) }}
-{{ with $resource }}
-{{ $.Scratch.Set "content" .Content }}
-{{ else }}
-{{/* Read the file relative to the content root. */}}
-{{ $resource := readFile $filename}}
-{{ with $resource }}{{ $.Scratch.Set "content" . }}{{ end }}
-{{ end }}
-{{ if not ($.Scratch.Get "content") }}
-{{ errorf "[%s] %q not found in %q" site.Language.Lang $fileDir.File $bundlePath }}
-{{ end }}
-{{ with $.Scratch.Get "content" }}
-<table class="includecode" id="{{ $file | anchorize }}">
-    <thead>
-        <tr>
-            <th>
-                {{ with $ghlink }}<a href="{{ . }}" download="{{ $file }}">{{ end }}
-                    <code>{{ $file }} {{ $bundlePath }}</code>
-                {{ if $ghlink }}</a>{{ end }}
-                <img src="{{ "images/copycode.svg" | relURL }}" style="max-height:24px" onclick="copyCode('{{ $file | anchorize }}')" title="Copy {{ $file }} to clipboard">
-            </th>
-        </tr>
-    </thead>
-    <tbody>
-        <tr>
-            <td>{{ highlight . $codelang "" }}  </td>
-        </tr>
-    </tbody>
-</table>
-{{ end }}