Remove detailed numpy build constraints

[adrianeboyd]

• Remove detailed numpy build constraints from pyproject.toml because it is too difficult to maintain for many architectures

  • These constraints are more a reflection of what is available on pypi as binary wheels rather than any real build requirements that it is necessary for users to follow when building from source
  • Users building their own binary packages will need to enforce the constraints that make sense in their environments, e.g., the conda compatible numpy pins

• Keep the build constraints in build-constraints.txt for use with our builds

  • Our builds with wheelwright are built against the earliest compatible binary versions of numpy on pypi
  • These constraints are documented within the distribution