doc: Fix dockerhub link in deployment-alternatives.rst
doc: Fix dockerhub link in deployment-alternatives.rst

This commit changed invalid link `https://registry.hub.docker.com/u/girder/girder/` to https://hub.docker.com/r/girder/girder
Kitware/girder,RafaelPalomar/girder,girder/girder,manthey/girder,RafaelPalomar/girder,manthey/girder,RafaelPalomar/girder,Kitware/girder,RafaelPalomar/girder,manthey/girder,girder/girder,manthey/girder,girder/girder,Kitware/girder,girder/girder,RafaelPalomar/girder,Kitware/girder