doc: mark Node 4 as EOL in changelog

Node 4 has been unsupported since 2018-05-01, but the changelog was out
of date and said that Node 4 was still in LTS.

PR-URL: #20926
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Weijia Wang <starkwang@126.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: Yuta Hiroto <hello@hiroppy.me>
Reviewed-By: Matheus Marchini <matheus@sthima.com>

CHANGELOG.md

@@ -29,7 +29,7 @@ release.
   <th><a href="doc/changelogs/CHANGELOG_V9.md">9</a></th>
   <th title="LTS Until 2019-12"><a href="doc/changelogs/CHANGELOG_V8.md">8</a><sup>LTS</sup></th>
   <th title="LTS Until 2019-04"><a href="doc/changelogs/CHANGELOG_V6.md">6</a><sup>LTS</sup></th>
-  <th title="LTS Until 2018-04"><a href="doc/changelogs/CHANGELOG_V4.md">4</a><sup>LTS</sup></th>
+  <th title="End-of-life since 2018-05-01"><a href="doc/changelogs/CHANGELOG_V4.md">4</a><sup>EOL</sup></th>
 </tr>
 <tr>
     <td valign="top">