extract-source fails due to modifications caused by .gitattributes

The pipeline fails for nvitop during the extract-source step since the repository contains .gitattributes which cause CR/LF modifications: https://salsa.debian.org/nvidia-team/nvitop/-/jobs/4857558

The repository is https://salsa.debian.org/nvidia-team/nvitop.git

At the time of the gbp setup-gitattributes call the working copy already contains CR/LF modifications, since the repository was initially cloned honoring .gitattributes. There is some kind of reset needed, to actually apply the new .git/info/gitattributes to the local checkout (effectively undoing to modifications done previously). Right now the modifications persist in uncommitted state, causing the subsequent git pull ... to fail.