SourceTextModule::AddAsyncParentModule can allocate so it must be a
static function.

Bug: chromium:1050433
Change-Id: I86e58569d16e626ce3f85cc46ea5f376c2d06f3f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2050383
Commit-Queue: Adam Klein <adamk@chromium.org>
Auto-Submit: Georg Neis <neis@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66228}