BLD: change section name in site.cfg.example from ALL to DEFAULT
BLD: change section name in site.cfg.example from ALL to DEFAULT

ALL is not meant for general use (although it does seem to work),
as documented in the docstring of `numpy.distutils.system_info`.

Closes gh-14746

[ci skip]

grlee77/scipy,endolith/scipy,tylerjereddy/scipy,WarrenWeckesser/scipy,andyfaff/scipy,rgommers/scipy,matthew-brett/scipy,zerothi/scipy,ilayn/scipy,mdhaber/scipy,rgommers/scipy,vigna/scipy,endolith/scipy,rgommers/scipy,Stefan-Endres/scipy,mdhaber/scipy,anntzer/scipy,zerothi/scipy,endolith/scipy,mdhaber/scipy,scipy/scipy,zerothi/scipy,andyfaff/scipy,tylerjereddy/scipy,WarrenWeckesser/scipy,zerothi/scipy,matthew-brett/scipy,matthew-brett/scipy,ilayn/scipy,ilayn/scipy,mdhaber/scipy,rgommers/scipy,grlee77/scipy,grlee77/scipy,matthew-brett/scipy,WarrenWeckesser/scipy,Stefan-Endres/scipy,mdhaber/scipy,WarrenWeckesser/scipy,ilayn/scipy,tylerjereddy/scipy,tylerjereddy/scipy,scipy/scipy,matthew-brett/scipy,Stefan-Endres/scipy,perimosocordiae/scipy,ilayn/scipy,endolith/scipy,grlee77/scipy,tylerjereddy/scipy,perimosocordiae/scipy,zerothi/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,vigna/scipy,andyfaff/scipy,perimosocordiae/scipy,perimosocordiae/scipy,anntzer/scipy,Stefan-Endres/scipy,grlee77/scipy,zerothi/scipy,vigna/scipy,mdhaber/scipy,andyfaff/scipy,endolith/scipy,andyfaff/scipy,Stefan-Endres/scipy,scipy/scipy,vigna/scipy,endolith/scipy,perimosocordiae/scipy,ilayn/scipy,andyfaff/scipy,Stefan-Endres/scipy,anntzer/scipy,scipy/scipy,anntzer/scipy,rgommers/scipy,vigna/scipy,scipy/scipy,anntzer/scipy,scipy/scipy,WarrenWeckesser/scipy,anntzer/scipy