Dedup code for generating prebuilt_stubs_sources in snapshot

Removes duplicated code for generating a versioned and non-versioned
form of the prebuilt_stubs_sources module in the snapshot.

Bug: 143678475
Test: m nothing

Change-Id: Ic431b6fcb6f3c7c85f1a04cb6f087424aaf0cffa
diff --git a/sdk/sdk_test.go b/sdk/sdk_test.go
index a4f54ef..e2e40bb 100644
--- a/sdk/sdk_test.go
+++ b/sdk/sdk_test.go
@@ -515,8 +515,8 @@
 
 prebuilt_stubs_sources {
     name: "myjavaapistubs",
-    srcs: ["java/myjavaapistubs_stubs_sources"],
     prefer: false,
+    srcs: ["java/myjavaapistubs_stubs_sources"],
 }
 
 cc_prebuilt_library_shared {