audio: Use 'sdk_version' instead of 'platform_apis'

Replace 'platform_apis: true' with 'sdk_version: module_current'.
The former causes compiling against SDK source code,
this is not needed for the audio HAL.

Bug: 205884982
Test: m android.hardware.audio.service-aidl.example
Change-Id: I9b9c32707ac7276f5cd077681bd1f8122bc20feb
diff --git a/audio/aidl/Android.bp b/audio/aidl/Android.bp
index 7db50d5..ebf5913 100644
--- a/audio/aidl/Android.bp
+++ b/audio/aidl/Android.bp
@@ -88,7 +88,7 @@
             enabled: false,
         },
         java: {
-            platform_apis: true,
+            sdk_version: "module_current",
         },
     },
 }