ci: Remove pip cache from setup-python

Building the python versions seems to work fine.
The new action fails with a missing 'requirements.txt', suppose (hope)
that is due to trying to cache with `pip`. Removes that line to try to
fix that.

.github/workflows/ci_build_and_test.yml

@@ -54,7 +54,6 @@ jobs:
         with:
           python-version: ${{ matrix.python-version }}
           cache-build: true
-          cache: pip
       - name: Install dependencies
         run: |
           pip install "numpy>=1.13.0,!=1.15.*"