Remove separate_platform_variant entries.

This no longer does anything.

Bug: 161456198
Test: build
Change-Id: I11329bd18de2f3e2f437fbcfd92e7a472be61070
diff --git a/omapi/aidl/Android.bp b/omapi/aidl/Android.bp
index 2b81200..d80317b 100644
--- a/omapi/aidl/Android.bp
+++ b/omapi/aidl/Android.bp
@@ -28,8 +28,5 @@
         rust: {
             enabled: true,
         },
-        ndk: {
-            separate_platform_variant: false,
-        },
     },
 }