[Support] Remove get getThreadCount (NFC) (#150786)
getThreadCount has been deprecated for more than a year since:
commit 744616b3aebd008a5ad0e9de9f82f5e284440ab1
Author: Mehdi Amini <joker.eph@gmail.com>
Date: Mon Feb 19 18:07:12 2024 -0800
This patch removes it.
