Change target sdk to system_current.

All telephony related components will target system_current as
part of mainline.

Test: treehugger
Bug: 145236086
Change-Id: If0516c88101db4978820d53e1bbd16a62124dcbd
diff --git a/proto/Android.bp b/proto/Android.bp
index 166be3d..d7e379f 100644
--- a/proto/Android.bp
+++ b/proto/Android.bp
@@ -22,8 +22,8 @@
         ],
     },
     srcs: ["src/**/*.proto"],
-    sdk_version: "core_platform",
+    sdk_version: "system_current",
     jarjar_rules: "jarjar-rules.txt",
     // Pin java_version until jarjar is certified to support later versions. http://b/72703434
     java_version: "1.8",
-}
\ No newline at end of file
+}