DOC: interpolate: details rectilinear grids in docstrings
DOC: interpolate: details rectilinear grids in docstrings

DOC: interpolate: details rectilinear grids in docstrings

Adds some clarifying language to the interpn and RegularGridInterpolator
docstrings relating to rectilinear grids.

gh-16126
scipy/scipy,WarrenWeckesser/scipy,scipy/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,rgommers/scipy,rgommers/scipy,anntzer/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,ilayn/scipy,mdhaber/scipy,rgommers/scipy,scipy/scipy,mdhaber/scipy,anntzer/scipy,andyfaff/scipy,andyfaff/scipy,andyfaff/scipy,WarrenWeckesser/scipy,endolith/scipy,andyfaff/scipy,mdhaber/scipy,endolith/scipy,rgommers/scipy,ilayn/scipy,ilayn/scipy,perimosocordiae/scipy,ilayn/scipy,endolith/scipy,anntzer/scipy,anntzer/scipy,endolith/scipy,anntzer/scipy,scipy/scipy,ilayn/scipy,perimosocordiae/scipy,mdhaber/scipy,perimosocordiae/scipy,scipy/scipy,andyfaff/scipy,andyfaff/scipy,endolith/scipy,anntzer/scipy,ilayn/scipy,perimosocordiae/scipy,rgommers/scipy,mdhaber/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,endolith/scipy,scipy/scipy,mdhaber/scipy,Stefan-Endres/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy