CI bsim workflow: Update changed-files action version

Dependabot has foud in a fork that we are using
a too old GitHub action version, which contains this
vulnerability:
https://www.cve.org/CVERecord?id=CVE-2023-51664
https://github.com/tj-actions/changed-files/security/advisories/GHSA-mcph-m25j-8j63



We do not use the output listing all changed files,
so we should not be exposed, but nonetheless,
let's update it.

Signed-off-by: Alberto Escolar Piedras <alberto.escolar.piedras@nordicsemi.no>