Revert "Disable --instruction-scheduling for mksnapshot"

This reverts commit 12b22b51.

Reason for revert: Experiment finished.

Original change's description:
> Disable --instruction-scheduling for mksnapshot
> 
> This is an experiment to see the memory/performance impact.
> 
> Bug: v8:9775
> Change-Id: I2ae61ae8bb5c6c1c55436e96c4b2d8201cbf4739
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1832177
> Reviewed-by: Michael Stanton <mvstanton@chromium.org>
> Commit-Queue: Georg Neis <neis@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#64062}

TBR=mvstanton@chromium.org,neis@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: v8:9775
Change-Id: Ife556af5f8c09c25f20756a9b2ac940cb74359e2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1855983Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Georg Neis <neis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64239}

BUILD.gn

@@ -1242,6 +1242,7 @@ template("run_mksnapshot") {
       "./" + rebase_path(get_label_info(":mksnapshot($v8_snapshot_toolchain)",
                                         "root_out_dir") + "/mksnapshot",
                          root_build_dir),
+      "--turbo_instruction_scheduling",
 
       # In cross builds, the snapshot may be generated for both the host and
       # target toolchains.  The same host binary is used to generate both, so