DEPS: possibly unnecessary scipy function checks

[jbrockmendel]

I'm seeing in test some things like

    try:
        from scipy.interpolate import pchip_interpolate  # noqa
    except ImportError:
        import pytest

        pytest.skip("scipy.interpolate.pchip missing")


def _skip_if_no_akima():
    try:
        from scipy.interpolate import Akima1DInterpolator  # noqa
    except ImportError:
        import pytest

        pytest.skip("scipy.interpolate.Akima1DInterpolator missing")

AFAICT pchip_interpolate goes back to at least scipy 0.13.0, and we require 0.19.0, so this check should be unnecessary (or more accurately, replaced with a skip_if_no_scipy). Not sure about akima, but we should track these down and put them all into test_decorators or compat or something