add use_course_url_slugs to prospectus_env_vars
add use_course_url_slugs to prospectus_env_vars

EDUlib/configuration,stvstnfrd/configuration,mitodl/configuration,appsembler/configuration,edx/configuration,arbrandes/edx-configuration,EDUlib/configuration,EDUlib/configuration,EDUlib/configuration,edx/configuration,mitodl/configuration,arbrandes/edx-configuration,edx/configuration,appsembler/configuration,appsembler/configuration,arbrandes/edx-configuration,appsembler/configuration,arbrandes/edx-configuration,mitodl/configuration,EDUlib/configuration,stvstnfrd/configuration,stvstnfrd/configuration,edx/configuration,arbrandes/edx-configuration,stvstnfrd/configuration,stvstnfrd/configuration,mitodl/configuration