[runtime] Always pretenure boilerplates.

This will simplify the optimizing compiler (no need to pretenure
COW arrays when compiling).

Bug: v8:7790
Change-Id: I7502f43c6b6f7e10bce8536352462731083b5bef
Reviewed-on: https://chromium-review.googlesource.com/1143466Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54566}

src/runtime/runtime-literals.cc

@@ -507,10 +507,7 @@ MaybeHandle<JSObject> CreateLiteral(Isolate* isolate,
       }
       return boilerplate;
     } else {
-      PretenureFlag pretenure_flag =
-          Heap::InNewSpace(*vector) ? NOT_TENURED : TENURED;
-      boilerplate =
-          Boilerplate::Create(isolate, description, flags, pretenure_flag);
+      boilerplate = Boilerplate::Create(isolate, description, flags, TENURED);
     }
     // Install AllocationSite objects.
     AllocationSiteCreationContext creation_context(isolate);