Improve staff_like_weight copy to indicate how the value is applied (PR #10726)

This PR is just updating the copy of the staff_like_weight setting, so no tests are included.

The change is intended to make it clear how the setting is used by Discourse. There is a discussion on Meta about it here: https://meta.discourse.org/t/staff-like-weight-0-or-1-to-match-regular-users/164374

GitHub

This pull request has been mentioned on Discourse Meta. There might be relevant details there:

https://meta.discourse.org/t/staff-like-weight-0-or-1-to-match-regular-users/164374/8