ci: Fix packdeps "cabal: Could not resolve dependencies"

There's no libxft-dev on the ubuntu-22.04 runner any more, so cabal
fails installing packdeps when invoked from a directory with
cabal.project.

.github/workflows/packdeps.yml

@@ -23,6 +23,7 @@ jobs:
         run: |
           set -ex
           echo "$HOME/.cabal/bin" >> $GITHUB_PATH
+          cd  # go somewhere without a cabal.project
           cabal install packdeps
       - name: Check package bounds (all)
         continue-on-error: true