Merge branch 'conda-ci-nodefaults' into 'master'

Use "nodefaults" in CI conda env file

See merge request inducer/pyopencl!110

.test-conda-env-py3.yml

 name: test-conda-env
 channels:
 - conda-forge
-- defaults
+- nodefaults
 
 dependencies:
 - python=3
 - git
-- conda-forge::numpy
+- numpy
 - pocl
 - mako
 - pybind11