Explain where the default password validation is

doc/security/password_length_limits.md

 # Custom password length limits
 
-If you want to enforce longer user passwords you can create an extra Devise initializer with the following steps:
+If you want to enforce longer user passwords you can create an extra Devise initializer with the steps below.
+If you do not use the `devise_password_length.rb` initializer the password length is set to a minimum of 8 characters in `config/initializers/devise.rb`.
 
 ```bash
 cd /home/git/gitlab