CI: install numpy from pip pandas-dev#36296 (pandas-dev#36323)

ci/build39.sh

@@ -3,16 +3,9 @@
 
 sudo apt-get install build-essential gcc xvfb
 pip install --no-deps -U pip wheel setuptools
-pip install python-dateutil pytz pytest pytest-xdist hypothesis
+pip install numpy python-dateutil pytz pytest pytest-xdist hypothesis
 pip install cython --pre # https://github.com/cython/cython/issues/3395
 
-git clone https://github.com/numpy/numpy
-cd numpy
-python setup.py build_ext --inplace
-python setup.py install
-cd ..
-rm -rf numpy
-
 python setup.py build_ext -inplace
 python -m pip install --no-build-isolation -e .