Enable Segoe Variable (#12462)

By adding another entry to our `maxversiontested`s.

Screenshots in #12452 (comment)

* [x] Closes #12452 
* [x] I work here
* [x] Docs are fine
* [x] Tests are fine

src/cascadia/WindowsTerminal/WindowsTerminal.manifest

@@ -14,6 +14,11 @@
         <!-- This will cause unpackaged activation failures in XAML Islands. -->
         <!-- (We use unpackaged activation in test scenarios.) See GH#10265. -->
         <maxversiontested Id="10.0.18362.0"/>
+
+        <!-- You apparently are expected to include all the maxversiontested
+        entries separately. They are treated like an array. This one turns on Segoe
+        UI Variable, GH #12452 -->
+        <maxversiontested Id="10.0.22000.0"/>
         <supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}" />
     </application>
   </compatibility>