There is no feature to prevent users from changing their own passwords.
If administrators wish to reduce the effort involved in password management, consider limiting the login method to Single Sign-On.
Related: Configure single sign-on (SSO) (Web Browser)
https://teachme.jp/8/manuals/11468504
Related: Limit user login to single sign-on (SSO) only (Web Browser)
https://teachme.jp/8/manuals/13209733