lower numpy requirement to 1.16 since that's the oldest version that …

…works with py3.7

.github/workflows/build.yml

@@ -111,9 +111,9 @@ jobs:
           pytest --cov cyvcf2 --cov-report term-missing
 
       - name: Test with oldest numpy that we support
-        if: contains(fromJson('["3.7", "3.8", "3.9"]'), matrix.python-version)
+        if: contains(fromJson('["3.7"]'), matrix.python-version)
         run: |
-          pip install --force-reinstall --no-cache-dir 'numpy==1.20.3'
+          pip install --force-reinstall --no-cache-dir 'numpy==1.16.0'
           pytest --cov cyvcf2 --cov-report term-missing
 
       - name: Test with newest available numpy

setup.py

@@ -290,7 +290,7 @@ def run(self):
         ],
     ),
     python_requires=">=3.7",
-    install_requires=["numpy>=1.20.3", "coloredlogs", "click"],
+    install_requires=["numpy>=1.16.0", "coloredlogs", "click"],
     include_package_data=True,
     zip_safe=False,
     cmdclass={