Merge branch 'psi-remove-remove-startup-css' into 'master'

Disable startup CSS

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/124406



Merged-by: Vasilii Iakliushin <viakliushin@gitlab.com>
Approved-by: Tomas Bulva <tbulva@gitlab.com>
Approved-by: Dzmitry Meshcharakou <12459192-dmeshcharakou@users.noreply.gitlab.com>
Approved-by: Vasilii Iakliushin <viakliushin@gitlab.com>
Reviewed-by: Simon Knox <simon@gitlab.com>
Reviewed-by: Dzmitry Meshcharakou <12459192-dmeshcharakou@users.noreply.gitlab.com>
Co-authored-by: Simon Knox <simon@gitlab.com>