Revert "[Gardener] Disable"

This reverts commit ec3452b13dc4790a43c39b1c5b71c730e124ff36.

Reason for revert: Cause CL reverted

Original change's description:
> [Gardener] Disable
> AwContentsGarbageCollectionTest#testActivityDoesNotLeak
>
> Bug: 344959459
> Change-Id: Ie88f907cb9fd709e5ad539217242241ae23f27b1
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5598440
> Reviewed-by: Shu Yang <shuyng@google.com>
> Owners-Override: Aishwarya Rajesh <aishwaryarj@google.com>
> Commit-Queue: Aishwarya Rajesh <aishwaryarj@google.com>
> Cr-Commit-Position: refs/heads/main@{#1310215}

Bug: 344959459
Change-Id: I8aff3393b7b78b772ab7330cdb41aaa85209fd35
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5598783
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Bo Liu <boliu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1310579}