Raw gist URLs follow the pattern below:
https://gist.githubusercontent.com/[gist username]/[gist ID]/raw/[gist commit ID]/[file name]
To view the latest version, simply remove the [gist commit ID] part:
https://gist.githubusercontent.com/[gist username]/[gist ID]/raw/[file name]
e.g.
https://gist.githubusercontent.com/mwek/9962f97f3bde157fd5dbd2b5dd0ec3ca/raw/user.js
Keep in mind that the endpoint is cached, so your updates may be visible with a slight delay.