Refs #11680 Fix AlignAndFocusPowder data link

Code/Mantid/docs/source/algorithms/AlignAndFocusPowder-v1.rst

@@ -42,7 +42,13 @@ Usage
 
 **Example: A simple Powgen example**
 
-The files needed for this example are not present in our standard usage data download due to their size.  They can however be downloaded using these links: `PG3_9830_event.nxs <https://github.com/mantidproject/systemtests/blob/master/Data/PG3_9830_event.nxs?raw=true>`_ and `pg3_mantid_det.cal <https://github.com/mantidproject/mantid/raw/master/Test/AutoTestData/pg3_mantid_det.cal>`_.
+The files needed for this example are not present in our standard usage data
+download due to their size.  They can however be downloaded using these links:
+`PG3_9830_event.nxs <https://github.com/mantidproject/systemtests/blob/master/Data/PG3_9830_event.nxs?raw=true>`_
+and
+`pg3_mantid_det.cal <http://198.74.56.37/ftp/external-data/MD5/e2b281817b76eadbc26a0a2617477e97>`_.
+
+You will have to rename :literal:`pg3_mantid_det.cal` manually, as its name in the link above is a list of random characters.
 
 .. code-block:: python