Fix apex_available on service-connectivity

arc-services depends on service-connectivity, so it also needs to be
available to the platform.

Bug: 183668370
Test: m
Change-Id: Id82125e98abf59b1cc8cb3fceab376597f0496ed
diff --git a/service/Android.bp b/service/Android.bp
index bccb224..b44128b 100644
--- a/service/Android.bp
+++ b/service/Android.bp
@@ -113,6 +113,7 @@
     ],
     jarjar_rules: "jarjar-rules.txt",
     apex_available: [
+        "//apex_available:platform", // For arc-services
         "com.android.tethering",
     ],
 }