Revert "[heap] Add flag to use high priority sweeping"

This reverts commit 0ae3b3b685a90b49ced486a8525c9e271dd715b4.

Reason for revert: doesn't fix the regression on pinpoint

Original change's description:
> [heap] Add flag to use high priority sweeping
>
> Use user blocking priority for new space sweeping in MinorMC.
> Sweeping of other spaces remains unchanged.
>
> Bug: v8:12612, chromium:1455769
> Change-Id: Ia895959ce3e3281fdf1a339135562fa62c235159
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4627103
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Omer Katz <omerkatz@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#88384}

Bug: v8:12612, chromium:1455769
Change-Id: Ie288ddd064eb1306a3a835d09588160a7a792adc
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4628073
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#88395}