Cannot reduce repo size
We're working on a game and we're storing the code and assets in a GitLab repo. We got this message on a push: GitLab: Your push to this repository would cause it to exceed the size limit of 11 GB so it has been rejected. Please contact your GitLab administrator for more information.
I removed 4GB of old assets from the master branch and tried to push again, but I got the same message.
Running housekeeping on the project did nothing.
On GitLab.com I also deleted a branch that held 1GB of assets, the repo size didn't go down. The branch was not merged into any other branches.
What is the correct way to reduce a repo size?