Drop CSP plugin-types spec reference & deprecate

w3c/webappsec-csp#394 completely removed the
plugin-types directive from the CSP spec. So it’s now deprecated and no
longer part of any current spec.

files/en-us/web/http/headers/content-security-policy/plugin-types/index.html

@@ -12,7 +12,7 @@
   - Plugins
   - Security
 ---
-<div>{{HTTPSidebar}}</div>
+<div>{{HTTPSidebar}}{{deprecated_header}}</div>
 
 <p>The HTTP {{HTTPHeader("Content-Security-Policy")}} (CSP)
   <code><strong>plugin-types</strong></code> directive restricts the set of plugins that
@@ -104,11 +104,6 @@ <h2 id="Specifications">Specifications</h2>
     </tr>
   </thead>
   <tbody>
-    <tr>
-      <td>{{specName("CSP 3.0", "#directive-plugin-types", "plugin-types")}}</td>
-      <td>{{Spec2('CSP 3.0')}}</td>
-      <td>No changes.</td>
-    </tr>
     <tr>
       <td>{{specName("CSP 1.1", "#directive-plugin-types", "plugin-types")}}</td>
       <td>{{Spec2('CSP 1.1')}}</td>