Drop `{{ pin_compatible("numpy") }}` from NumPy docs

[jakirkham]

As numpy already contains a run_exports, which has been present since numpy version 1.22.3 number 1 ( conda-forge/numpy-feedstock#262 ), and conda-forge is using numpy version 1.22 or newer, we can just rely on run_exports from numpy

Given this, {{ pin_compatible("numpy") }} is no longer needed in the NumPy doc recommendations. So we should drop it

We may consider mentioning the history of it

[h-vetinari]

which has been present since numpy version 1.22.3 number 1

It got backported all the way back to 1.19.