DOC: added mention of the limitations of Thomas' algorithm (#14638)
DOC: added mention of the limitations of Thomas' algorithm (#14638)

* DOC: added mention of the limitations of Thomas' algorithm

Co-authored-by: Matt Haberland <1f6e3f9dd4f3b851e1c9f994a33220fb712394f1@calpoly.edu>
ilayn/scipy,WarrenWeckesser/scipy,mdhaber/scipy,scipy/scipy,Stefan-Endres/scipy,andyfaff/scipy,ilayn/scipy,mdhaber/scipy,anntzer/scipy,andyfaff/scipy,scipy/scipy,Stefan-Endres/scipy,mdhaber/scipy,ilayn/scipy,mdhaber/scipy,Stefan-Endres/scipy,ilayn/scipy,anntzer/scipy,scipy/scipy,WarrenWeckesser/scipy,scipy/scipy,andyfaff/scipy,endolith/scipy,scipy/scipy,endolith/scipy,Stefan-Endres/scipy,ilayn/scipy,andyfaff/scipy,endolith/scipy,WarrenWeckesser/scipy,mdhaber/scipy,anntzer/scipy,anntzer/scipy,endolith/scipy,anntzer/scipy,ilayn/scipy,endolith/scipy,andyfaff/scipy,anntzer/scipy,WarrenWeckesser/scipy,WarrenWeckesser/scipy,scipy/scipy,Stefan-Endres/scipy,endolith/scipy,Stefan-Endres/scipy,mdhaber/scipy,WarrenWeckesser/scipy,andyfaff/scipy