Update shaking.TreeShakingSpecificTest to recent change:

The proguard map output now contains line numbers.

Bug:
Change-Id: If21a6d5d9de7ec01f1f39c4cf8e5d332f0b62cd7
diff --git a/src/test/examples/shaking1/print-mapping.ref b/src/test/examples/shaking1/print-mapping.ref
index b75dbd3..6500a8d 100644
--- a/src/test/examples/shaking1/print-mapping.ref
+++ b/src/test/examples/shaking1/print-mapping.ref
@@ -1,4 +1,4 @@
 shaking1.Shaking -> shaking1.Shaking:
 shaking1.Used -> a.a:
     java.lang.String name -> a
-    java.lang.String method() -> a
+    17:17:java.lang.String method() -> a