Bump the NumPy pin in preparation for aarch64 and ppc64le builds

[jakirkham]

This is analogous to PR ( https://github.com/conda-forge/arrow-cpp-feedstock/pull/99 ) except for pyarrow instead.

In preparation for building this feedstock for aarch64 and ppc64le, bump the numpy minimum version to 1.16, which is the version we have built on those architectures. It was found to be too difficult to build earlier versions on those architectures; so, the minimum numpy version was bumped to the oldest version that could reasonably be built.

ref: https://github.com/conda-forge/numpy-feedstock/pull/136#issuecomment-510785440

cc @xhochy

Checklist

• [x] Used a fork of the feedstock to propose changes
• [x] Bumped the build number (if the version is unchanged)
• [ ] Reset the build number to 0 (if the version changed)
• [x] Re-rendered with the latest conda-smithy (Use the phrase code>@<space/conda-forge-admin, please rerender in a comment in this PR for automated rerendering)
• [x] Ensured the license file is being packaged.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[jakirkham]

This now passes! 😄