conda-recipe: Remove explicit host numpy pinning

Let default conda-build provide the build numpy version. This fixes
builds for Python 3.9 and up.

Author: ales-erjavec

conda-recipe/meta.yaml

@@ -28,7 +28,7 @@ requirements:
   host:
     - python
     - setuptools
-    - numpy         1.14.*
+    - numpy
     - cython
     - pip
     - wheel