DOC: Fewer blank lines in PR template
DOC: Fewer blank lines in PR template

Reduce the need to scroll, per @mattip suggestion in #17440

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