Revert "mac: Forcibly disable Apple’s “Probabilistic Guard Malloc”"

This reverts commit 340be9daf6487e9ead5565f74543cde8bdfc3aac.

Reason for revert: Suspicious for causing consistent test failures on mac64 builder
i.e. https://ci.chromium.org/ui/p/chrome/builders/ci/mac64/228377/overview

Bug: 414750473
Original change's description:
> mac: Forcibly disable Apple’s “Probabilistic Guard Malloc”
>
> “Probabilistic Guard Malloc” is normally disabled for non-Apple
> executables when not running on Apple-internal OS builds. When
> restarting Chrome from the macOS-provided “quit unexpectedly” dialog
> after a browser crash, this malloc feature will be enabled, as observed
> on macOS 15.4.1. Code inspection shows that this may be a new behavior
> in macOS 15.3, although this is not dispositive, because only libmalloc
> source is public, and there are other OS components in the chain that
> are not.
>
> Chrome is unable to launch with this malloc feature enabled, and crashes
> during early startup, while loading the framework. From the user’s
> perspective, when choosing to restart Chrome from the OS crash dialog,
> this results in a secondary (and subsequent) crash.
>
> It’s possible to forcibly disable this malloc feature by environment
> variable. The environment variable can be set in the app’s Info.plist.
> While environment variables are only set from Info.plist when launched
> via Launch Services (and not, for example, from a shell), the launch
> from the macOS crash dialog does go through Launch Services, so this
> should be a complete fix.
>
> Bug: 414750473
> Change-Id: I0a9aba7d1ea0b94327252a706ddba686799d4863
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6501000
> Reviewed-by: Avi Drissman <avi@chromium.org>
> Commit-Queue: Mark Mentovai <mark@chromium.org>
> Reviewed-by: Marijn Kruisselbrink <mek@chromium.org>
> Reviewed-by: Leonard Grey <lgrey@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1454086}

Bug: 414750473
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I99f9434df068e8741ff15ca5b5ce6759b4df1e18
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6502113
Auto-Submit: Nidhi Jaju <nidhijaju@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Nidhi Jaju <nidhijaju@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1454260}