Revert "cppgc: Enable pointer compression by default on Desktop"

This reverts commit 4cf08c1a.

Reason for revert: broke ubsan.

Original change's description:
> cppgc: Enable pointer compression by default on Desktop
>
> The CL enables pointer compression in Oilpan.
>
> For sherrifs: the CL may cause some slight perf regressions (likely
> blink_perf.*), due to slightly higher cost of compression and
> decomrpession.
>
> Speedometer2 is not expected to regress, as was checked locally. Such a
> slight performance degradation is compensated by memory savings that are
> expected to be around 10-20% of Oilpan committed size (~2.5-5% of Renderer
> PMF).
>
> Bug: chromium:1325007
> Change-Id: I2e31fc56250dbe6354a7614fa1f9e926260d842b
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3695565
> Commit-Queue: Anton Bikineev <bikineev@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#81442}

Bug: chromium:1325007
Change-Id: Iabc31ed683841ba0189dee9028da330dc03d7e09
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3735168
Auto-Submit: Anton Bikineev <bikineev@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81443}

BUILD.gn

@@ -812,12 +812,6 @@ if (cppgc_enable_caged_heap) {
 
   # Always enable young generation compile time flag if caged heap is enabled.
   cppgc_enable_young_generation = true
-
-  if (is_linux || is_mac || is_win) {
-    # Always enable on desktop but avoid on ChromeOS for now (for stability
-    # reasons).
-    cppgc_enable_pointer_compression = true
-  }
 }
 if (cppgc_enable_young_generation) {
   enabled_external_cppgc_defines += [ "CPPGC_YOUNG_GENERATION" ]