Remove outdated content

Author: MetRonnie

src/workflow-design-guide/efficiency.rst

@@ -346,11 +346,6 @@ Optional app configs should be valid on top of the main app config and not
 dependent on the use of other optional app configs. This ensures they will
 work correctly with macros and can therefore be upgraded automatically.
 
-.. note::
-
-   Currently optional configs don't work very well with UM STASH
-   configuration - see :ref:`UM STASH in Optional App Configs`.
-
 Optional app configs can be loaded by command line switch:
 
 .. code-block:: bash

src/workflow-design-guide/portable-workflows.rst

@@ -54,7 +54,7 @@ Site Include-Files
 
 If a section heading in a :cylc:conf:`flow.cylc` file is repeated the items
 under it simply add to or override those defined under the same section earlier
-in the file (but note :ref:`List Item Override In Site Include-Files`).
+in the file.
 For example, this task definition:
 
 .. code-block:: cylc