Fix export CI test

Not entirely sure why this is only a problem now, but
`matrix.python-version` isn't defined.

Author: erikjohnston

.github/workflows/tests.yml

@@ -283,7 +283,6 @@ jobs:
       - run: sudo apt-get -qq install xmlsec1
       - uses: matrix-org/setup-python-poetry@v1
         with:
-          python-version: ${{ matrix.python-version }}
           extras: "postgres"
       - run: .ci/scripts/test_export_data_command.sh