Revert "[wx] Keep the execute bit while making code writable"

This reverts commit 3094d598.

Reason for revert: Breaks on Mac arm64:
https://ci.chromium.org/p/v8/builders/ci/V8%20Mac%20-%20arm64%20-%20release/3109

Original change's description:
> [wx] Keep the execute bit while making code writable
>
> Otherwise SMC perturbs the icache too much it seems.
>
> Change-Id: Iceea779a7e3deee90efe29df568732d6ac5bcffa
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2753768
> Commit-Queue: Toon Verwaest <verwaest@chromium.org>
> Auto-Submit: Toon Verwaest <verwaest@chromium.org>
> Reviewed-by: Hannes Payer <hpayer@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#73355}

Change-Id: I4e85f6308ca22e366cdad4b621d233c3b1e3ed90
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2756539
Auto-Submit: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#73378}

include/v8-platform.h

@@ -408,6 +408,7 @@ class PageAllocator {
     kNoAccess,
     kRead,
     kReadWrite,
+    // TODO(hpayer): Remove this flag. Memory should never be rwx.
     kReadWriteExecute,
     kReadExecute,
     // Set this when reserving memory that will later require kReadWriteExecute

src/heap/memory-chunk.cc

@@ -91,7 +91,7 @@ void MemoryChunk::SetReadAndWritable() {
     DCHECK(IsAligned(unprotect_start, page_size));
     size_t unprotect_size = RoundUp(area_size(), page_size);
     CHECK(reservation_.SetPermissions(unprotect_start, unprotect_size,
-                                      PageAllocator::kReadWriteExecute));
+                                      PageAllocator::kReadWrite));
   }
 }