fix a test that turned off lexical borrow scopes for seemingly no reason.

Author: kavon

test/SILOptimizer/allocbox_to_stack_noncopyable.sil

@@ -1,4 +1,4 @@
-// RUN: %target-sil-opt -enable-experimental-move-only -enable-sil-verify-all %s -allocbox-to-stack -enable-copy-propagation=requested-passes-only -enable-lexical-borrow-scopes=false | %FileCheck %s
+// RUN: %target-sil-opt -enable-experimental-move-only -enable-sil-verify-all %s -allocbox-to-stack -enable-copy-propagation=requested-passes-only | %FileCheck %s
 
 sil_stage raw
 
@@ -159,4 +159,4 @@ bb2:
 bb3:
   %30 = tuple ()
   return %30 : $()
-}
+}