Enable PeopleSpaceActivity by default.

We were previously enabling the activity via flag,
but we're not using the flag anymore.

Change-Id: I02494a3ff9dfc591dbe49473283ce5a46ad226d6
Test: manual
Bug: 176094791

packages/SystemUI/AndroidManifest.xml

@@ -570,6 +570,7 @@
         <!-- People Space UI Screen -->
         <activity android:name=".people.PeopleSpaceActivity"
             android:label="People"
+            android:enabled="true"
             android:exported="true"
             android:theme="@android:style/Theme.Material.NoActionBar">
             <intent-filter>