Restrict MANAGE_DEVICE_ADMIN permissions to signature

We want to prevent privileged apps from calling DevicePolicyManager#setActiveAdmin. After this, only apps signed with the platform certificate (e.g Settings / ManagedProvisioning) will be allowed to set Device Admins.

Leave @SystemApi so that it is clear that it 'was' a privileged permission, but add @removed to show that it is no longer a privileged permission.

Bug: 111153365
Test: atest PermissionsHostTest && atest CtsAdminTestCases
Change-Id: I688e87cf09ad206f4f517a7be960c2aa01af8fc4
diff --git a/api/system-removed.txt b/api/system-removed.txt
index 4beb699..5a7ec8b 100644
--- a/api/system-removed.txt
+++ b/api/system-removed.txt
@@ -1,3 +1,11 @@
+package android {
+
+  public static final class Manifest.permission {
+    field public static final java.lang.String MANAGE_DEVICE_ADMINS = "android.permission.MANAGE_DEVICE_ADMINS";
+  }
+
+}
+
 package android.app {
 
   public class Notification implements android.os.Parcelable {