Revert "[test] Disable flaky cctest on stress_concurrent_allocation"

This reverts commit 336673f4.

Reason for revert: Verifying a fix - https://chromium-review.googlesource.com/c/v8/v8/+/2853587

Original change's description:
> [test] Disable flaky cctest on stress_concurrent_allocation
>
> Bug: v8:11695
> Change-Id: I3b558260a23b4fb7d16bc8f1e9c57b94bce03838
> No-Try: true
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2854299
> Reviewed-by: Leszek Swirski <leszeks@chromium.org>
> Auto-Submit: Maya Lekova <mslekova@chromium.org>
> Commit-Queue: Maya Lekova <mslekova@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74228}

Bug: v8:11695
Change-Id: Iab080de98a6f2b96f98104bec4f96e0331de4573
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2854746
Auto-Submit: Maya Lekova <mslekova@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@{#74246}

test/cctest/cctest.status

@@ -725,13 +725,6 @@
   'test-heap/ObjectsInEagerlyDeoptimizedCodeAreWeak': [PASS, FAIL],
 }], # variant == stress_concurrent_inlining
 
-################################################################################
-['variant == stress_concurrent_allocation', {
-  # BUG(11695): Crashing flakily.
-  'test-serialize/StartupSerializerTwiceRunScript': [PASS, FAIL],
-}], # variant == stress_concurrent_allocation
-
-
 ################################################################################
 ['third_party_heap', {
   # v8::Unwinder::PCIsInV8 is not supported