Mark all features from DNT spec deprecated (#4960)

The https://www.w3.org/TR/tracking-dnt/ spec never made it to W3C
Recommendation; instead it was retired as a W3C Working Group Note:

https://www.w3.org/TR/2019/NOTE-tracking-dnt-20190117/

In the W3C spec database its formal status is Retired:

https://www.w3.org/TR/?tag=privacy&status=ret

And the Status section of https://www.w3.org/TR/tracking-dnt/ itself says:

> Since its last publication as a Candidate Recommendation, there has
> not been sufficient deployment of these extensions (as defined) to
> justify further advancement, nor have there been indications of planned
> support among user agents, third parties, and the ecosystem at large.

All of that is sufficient to merit the features being marked as
deprecated in BCD.

So this change adds a Deprecated banner to the following articles:

* https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/DNT
* https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Tk
* https://developer.mozilla.org/en-US/docs/Web/API/Navigator/doNotTrack

Related BCD change: mdn/browser-compat-data#10469

files/en-us/web/api/navigator/donottrack/index.html

@@ -9,7 +9,7 @@
   - Property
   - Reference
 ---
-<div>{{ApiRef("HTML DOM")}}</div>
+<div>{{ApiRef("HTML DOM")}}{{Deprecated_header}}</div>
 
 <p>The <code><strong>Navigator.doNotTrack</strong></code> property returns the user's Do Not Track setting, which indicates whether the user is requesting web sites and advertisers to not track them.</p>
 

files/en-us/web/http/headers/dnt/index.html

@@ -7,7 +7,7 @@
 - Reference
 - header
 ---
-<div>{{HTTPSidebar}}</div>
+<div>{{HTTPSidebar}}{{Deprecated_header}}</div>
 
 <p>The <strong><code>DNT</code></strong> (<strong>D</strong>o <strong>N</strong>ot
   <strong>T</strong>rack) request header indicates the user's tracking preference. It lets

files/en-us/web/http/headers/index.html

@@ -201,15 +201,6 @@ <h2 id="CORS">CORS</h2>
  <dd>Specifies origins that are allowed to see values of attributes retrieved via features of the <a href="/en-US/docs/Web/API/Resource_Timing_API">Resource Timing API</a>, which would otherwise be reported as zero due to cross-origin restrictions.</dd>
 </dl>
 
-<h2 id="Do_Not_Track">Do Not Track</h2>
-
-<dl>
- <dt>{{HTTPHeader("DNT")}}</dt>
- <dd>Expresses the user's tracking preference.</dd>
- <dt>{{HTTPHeader("Tk")}}</dt>
- <dd>Indicates the tracking status of the corresponding response.</dd>
-</dl>
-
 <h2 id="Downloads">Downloads</h2>
 
 <dl>

files/en-us/web/http/headers/tk/index.html

@@ -9,7 +9,7 @@
 - header
 - tracking
 ---
-<div>{{HTTPSidebar}}</div>
+<div>{{HTTPSidebar}}{{Deprecated_header}}</div>
 
 <p>The <strong><code>Tk</code></strong> response header indicates the tracking status that
   applied to the corresponding request.</p>

files/en-us/web/http/resources_and_specifications/index.html

@@ -248,11 +248,6 @@
     <em>Defines extensions of HTTP for Server-Sent Events</em></td>
    <td>{{Spec2("HTML WHATWG")}}</td>
   </tr>
-  <tr>
-   <td><a href="https://www.w3.org/2011/tracking-protection/drafts/tracking-dnt.html">Tracking Preference Expression</a></td>
-   <td>DNT header</td>
-   <td>Editor's draft / Candidate recommendation</td>
-  </tr>
   <tr>
    <td><a href="https://wicg.github.io/reporting/">Reporting API</a></td>
    <td><code>Report-To</code> header</td>