DOC, BLD: sphinx 2.2.0 -> 2.3.1 to get rid of deprecation warning
DOC, BLD: sphinx 2.2.0 -> 2.3.1 to get rid of deprecation warning

endolith/numpy,mattip/numpy,jakirkham/numpy,jakirkham/numpy,grlee77/numpy,madphysicist/numpy,abalkin/numpy,numpy/numpy,pbrod/numpy,simongibbons/numpy,madphysicist/numpy,rgommers/numpy,seberg/numpy,seberg/numpy,grlee77/numpy,charris/numpy,rgommers/numpy,simongibbons/numpy,madphysicist/numpy,madphysicist/numpy,charris/numpy,rgommers/numpy,anntzer/numpy,WarrenWeckesser/numpy,madphysicist/numpy,endolith/numpy,rgommers/numpy,mhvk/numpy,mhvk/numpy,pbrod/numpy,charris/numpy,mhvk/numpy,pbrod/numpy,numpy/numpy,seberg/numpy,anntzer/numpy,jakirkham/numpy,WarrenWeckesser/numpy,abalkin/numpy,grlee77/numpy,mattip/numpy,simongibbons/numpy,anntzer/numpy,mhvk/numpy,abalkin/numpy,anntzer/numpy,jakirkham/numpy,WarrenWeckesser/numpy,grlee77/numpy,mhvk/numpy,pdebuyl/numpy,pdebuyl/numpy,numpy/numpy,simongibbons/numpy,endolith/numpy,numpy/numpy,simongibbons/numpy,mattip/numpy,seberg/numpy,mattip/numpy,pdebuyl/numpy,charris/numpy,WarrenWeckesser/numpy,pbrod/numpy,pbrod/numpy,jakirkham/numpy,WarrenWeckesser/numpy,endolith/numpy,grlee77/numpy,pdebuyl/numpy