Revert "[ext-code-space] Enable external code space on x64 and desktop arm64"

This reverts commit 7fc4868e.

Reason for revert: https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Clusterfuzz%20Linux64%20-%20release%20builder/26331/overview

Original change's description:
> [ext-code-space] Enable external code space on x64 and desktop arm64
>
> Perf Sheriffs: this CL might regress some benchmarks while improving
> the others.
>
> Bug: v8:11880
> Change-Id: Iddaba0512100eedf61d8b106da0be0a08d273b67
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3412072
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Commit-Queue: Igor Sheludko <ishell@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#78743}

Bug: v8:11880
Change-Id: I238bb143b3781fc0b865edf4e7cb0ae52cbad0c7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3412078
Auto-Submit: Nico Hartmann <nicohartmann@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Nico Hartmann <nicohartmann@chromium.org>
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/main@{#78744}

BUILD.gn

@@ -412,9 +412,7 @@ if (v8_enable_short_builtin_calls == "") {
       v8_current_cpu == "x64" || (!is_android && v8_current_cpu == "arm64")
 }
 if (v8_enable_external_code_space == "") {
-  v8_enable_external_code_space =
-      v8_enable_pointer_compression &&
-      (v8_current_cpu == "x64" || (!is_android && v8_current_cpu == "arm64"))
+  v8_enable_external_code_space = false
 }
 if (v8_enable_single_generation == "") {
   v8_enable_single_generation = v8_disable_write_barriers