[doc]Fix an invalid url link in docs
This is to fix an invalid url link in docs.
@@ -289,7 +289,7 @@ Add ``volumes`` field to group list/detail and group show.
3.27 (Maximum in Ocata)
-----------------------
Added new attachment APIs. See the
-`API reference <https://docs.openstack.org/api-ref/block-storage/v3/index.html#attachments>`__
+`API reference <https://docs.openstack.org/api-ref/block-storage/v3/index.html#attachments-attachments>`__
for details.
3.28
