Change SystemApi as per API council feedback

API council have requested a manifest constant be added
to the SystemApi directly in preference to an indirect
SystemApi constant here:
android.provider.TimeZoneRulesDataContract.READER_PERMISSION.

This is the first of three changes to (1) add the new constant,
(2) switch over code using the constant, (3) remove the
constant.

Bug: 64568899
Test: None, build only
Change-Id: Ib9766591979886d1db3b1d7321536dabf5cf81a8
diff --git a/core/res/AndroidManifest.xml b/core/res/AndroidManifest.xml
index 2652930..2954d5e 100644
--- a/core/res/AndroidManifest.xml
+++ b/core/res/AndroidManifest.xml
@@ -2273,7 +2273,7 @@
          <p>An application requesting this permission is responsible for
          verifying the source and integrity of the update before passing
          it off to the installer components.
-         @hide -->
+         @SystemApi @hide -->
     <permission android:name="android.permission.UPDATE_TIME_ZONE_RULES"
         android:protectionLevel="signature|privileged" />