.github: workflows: test-plans-pipeline: pin pytest to 8.0.0

Pipeline fails with 8.0.1 of pytest.

Signed-off-by: Anders Roxell <anders.roxell@linaro.org>

.github/workflows/test-plans-pipeline.yml

@@ -23,7 +23,7 @@ jobs:
          pip install flit
          pip install tuxpkg
          pip install py
-         pip install pytest
+         pip install pytest==8.0.0
          pip install pytest-cov
          pip install pytest-parallel
          export FLIT_ROOT_INSTALL=1