Set prebuilt_apis java_imports sdk_version to none

Bug: 160455085
Test: m
Change-Id: I9057e68d7e01f0a339113383b92bfe860688bc7c
diff --git a/Android.bp b/Android.bp
index eb75614..d3c9831 100644
--- a/Android.bp
+++ b/Android.bp
@@ -112,4 +112,5 @@
         "29",
         "current",
     ],
+    imports_sdk_version: "none",
 }