releases/lts: correct v3.20 last minor

Right now, the no longer maintained table suggests that the last release
for the 3.20 LTS was 3.20.3. This is incorrect, as 3.20.6 was released
in November of 2020. Let's update this table to reflect that.

Author: Geodewd549

app/templates/releases/lts.hbs

@@ -108,8 +108,8 @@
     </tr>
     <tr>
       <td>3.20</td>
-      <td>3.20.3</td>
-      <td>August 2020</td>
+      <td>3.20.6</td>
+      <td>November 2020</td>
     </tr>
     <tr>
       <td>3.16</td>