Using common apex_defaults for com.android.cellbroadcast module.

In /packages/modules/common/sdk/ModuleDefaults.bp file, some
apex_defaults are added to provide common parameters corresponding to
Q, R, S, and T releases.
(Refer to CL link for above mentioned change -
https://android-review.googlesource.com/c/platform/packages/modules/common/+/2005890?forceReload=true)

This CL is using the apex_default corresponding to R release for the
com.google.android.cellbroadcast module.

Bug: 172589606
Test: USE_RBE=true m
Since there are no runtime changes, successful code build is enough for
testing.

Change-Id: Ie30d1e419ae4a8c83f80c27b5cef5785b8e49d21
diff --git a/apex/Android.bp b/apex/Android.bp
index c5e7854..614c106 100644
--- a/apex/Android.bp
+++ b/apex/Android.bp
@@ -5,8 +5,7 @@
 
 apex_defaults {
     name: "com.android.cellbroadcast-defaults",
-    updatable: true,
-    min_sdk_version: "30",
+    defaults: ["r-launched-apex-module"],
 
     manifest: "apex_manifest.json",