Remove link to the old documentation

Packagers should include those in the package, as ADMIN.md...

tools/README-generator/templates/README.md.j2

@@ -72,7 +72,6 @@ If you don't have YunoHost, please consult [the guide](https://yunohost.org/#/in
 {% endif -%}
 {% if upstream.code -%}* Upstream app code repository: <{{ upstream.code }}>
 {% endif -%}
-* YunoHost documentation for this app: <https://yunohost.org/app_{{manifest.id}}>
 * Report a bug: <https://github.com/YunoHost-Apps/{{manifest.id}}_ynh/issues>
 
 ## Developer info