MAINT: Update PyPy version used by CI
MAINT: Update PyPy version used by CI

Use PyPy 7.3.4 instead of 7.3.4rc1.

simongibbons/numpy,pbrod/numpy,endolith/numpy,anntzer/numpy,seberg/numpy,pdebuyl/numpy,endolith/numpy,numpy/numpy,simongibbons/numpy,numpy/numpy,seberg/numpy,mattip/numpy,anntzer/numpy,numpy/numpy,rgommers/numpy,mhvk/numpy,jakirkham/numpy,simongibbons/numpy,jakirkham/numpy,charris/numpy,simongibbons/numpy,mhvk/numpy,anntzer/numpy,numpy/numpy,seberg/numpy,pbrod/numpy,mattip/numpy,pdebuyl/numpy,jakirkham/numpy,jakirkham/numpy,mhvk/numpy,mattip/numpy,rgommers/numpy,charris/numpy,pdebuyl/numpy,endolith/numpy,rgommers/numpy,rgommers/numpy,pbrod/numpy,mattip/numpy,pbrod/numpy,pbrod/numpy,endolith/numpy,mhvk/numpy,anntzer/numpy,simongibbons/numpy,charris/numpy,seberg/numpy,charris/numpy,mhvk/numpy,jakirkham/numpy,pdebuyl/numpy