hooks/install: use python3.8

We're upgrading python in boards to python3.11, but want to continue
using python3.8 in the SDK for now.

BUG=b/389105832
TEST=presubmit
RELEASE_NOTE=None

Change-Id: I7a508102ef192be260eab34746ba0358c1b0c716
Reviewed-on: https://cos-review.googlesource.com/c/third_party/platform/crosutils/+/94686
Reviewed-by: Kevin Berry <kpberry@google.com>
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>