Removes UniversalBGTask Activation class from framework manifest (#4863)

Signed-off-by: godlytalias <[email protected]>

Author: godlytalias

build/NuSpecs/AppxManifest.xml

@@ -25,12 +25,6 @@
           <ActivatableClass ActivatableClassId="Microsoft.Windows.Globalization.ApplicationLanguages" ThreadingModel="both" />
       </InProcessServer>
     </Extension>
-    <Extension Category="windows.activatableClass.inProcessServer">
-      <InProcessServer>
-        <Path>Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.dll</Path>
-        <ActivatableClass ActivatableClassId="Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.Task" ThreadingModel="both" />
-      </InProcessServer>
-    </Extension>
     <Extension Category="windows.activatableClass.inProcessServer">
       <InProcessServer>
         <Path>Microsoft.WindowsAppRuntime.dll</Path>