Fix one more occurence

build_tools/circle/install_from_sdist.sh

@@ -4,7 +4,7 @@ set -e
 
 # we'll need numpy and cython to build this. let install_requires do all the
 # rest of the work.
-pip install "numpy>=1.16" "cython>=0.29,!=0.29.18"
+pip install "numpy~=1.19" "cython>=0.29,!=0.29.18"
 python setup.py sdist
 
 # it will always be 0.0.0 since we didn't version it