Since I was the one suggesting it in #18716, I kinda volunteered to implement
it. This improvement is based on [Censys's blogpost](https://censys.com/cve-2021-22205-it-was-a-gitlab-smash/)
on the topic, making use of the `/assets/application-….css` files that have
a unique name per gitlab versions.
The fingerprints were acquired with this bash script:
```bash
assetdir="/opt/gitlab/embedded/service/gitlab-rails/public/assets"
tags=$(curl "https://hub.docker.com/v2/repositories/gitlab/gitlab-ce/tags?page_size=100" | jq -r '.results[].name')
for tag in $tags; do
filename=$(docker run --quiet --rm -it --entrypoint "" gitlab/gitlab-ce:$tag ls $assetdir|egrep '^application-.*\.css' | grep -v \.gz | cut -d' ' -f1)
echo $tag,$filename
done
```
Co-authored-by: cgranleese-r7 <69522014+cgranleese-r7@users.noreply.github.com>
cgranleese-r7