Update TF-M maintainers list.

TF-M maintainers have changed recently and reflected in TF-M documentation, but Gerrit keeps assigning the old maintainers. Antonio made changes for that in this patch: https://git.trustedfirmware.org/TF-M/+/refs/heads/main/reviewers.config but it seems to have no effect.
@Arthur She, could you take a look? In the past, you were lucky to make the same change.