This can be done, but to change all uses of “Admins” and “Moderators” you will need to update quite a few translation keys.
To make the change, go to your Admin / Customize / Text page and search for the word you are wanting to change. If you are trying to change the title of the Moderators group, you need to search for the text that is used for Moderators in the language that you are using on the site. For example, if your site is in Portuguese, you will need to search for the word “Moderadores”. That should return a lot of results.
There is a way to find the exact translation key for text that is used on Discourse. It is done by enabling verbose localization. There are details about that approach here: Find a translation key with verbose localization. Using verbose localization will allow you to find almost all translation keys on Discourse. A case where it doesn’t work is trying to find the group names that are shown in these two screenshots:
The translation keys used for Moderators in those screenshots are js.about.moderators and groups.default_names.moderators.