[MAINT] Update old CI steps (#214)

Author: tsbinns

.github/workflows/unit_tests.yml

@@ -126,17 +126,14 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip setuptools wheel
-          pip install --upgrade --upgrade-strategy eager .[test]
+          pip install -e . --no-deps
+          pip install -r tools/requirements_old.txt
       - name: Display versions and environment information
         run: |
           echo $TZ
           date
-          python --version
           which python
-      - run: |
-          pip install -e . --no-deps
-          pip install -r tools/requirements_old.txt
-      - run: python -c "import pybispectra; import mne; print(f'PyBispectra {pybispectra.__version__}\n'); mne.sys_info()"
+          python -c "import pybispectra; import mne; print(f'PyBispectra {pybispectra.__version__}\n'); mne.sys_info()"
       - name: Download testing data
         run: python -c "from pybispectra.utils import DATASETS, get_example_data_paths; (get_example_data_paths(data) for data in DATASETS.keys())"
       - name: Run pytest