We lost sphinx.po that was already translated

For some reason, https://github.com/PyCampES/python-docs-es/blob/3.7/sphinx.po was deleted completely at https://github.com/PyCampES/python-docs-es/commit/6b86caffe380c7101b6ec26eeccfaaaf087c91c5#diff-45573348f1c20fa58a6bb5ae4fbeb851

We should recover it because it was used to translated the index and other sections that are outside .rst files.