fix: broken link to developer stack in README.rst
fix: broken link to developer stack in README.rst

Make the text in paragraph the same as in the link definition.

eduNEXT/edx-platform,eduNEXT/edx-platform,arbrandes/edx-platform,angelapper/edx-platform,arbrandes/edx-platform,angelapper/edx-platform,angelapper/edx-platform,eduNEXT/edx-platform,angelapper/edx-platform,arbrandes/edx-platform,eduNEXT/edx-platform,arbrandes/edx-platform