Fix broken links (#1298)

Fix some broken hyperlinks in the rst documentation.

doc/concepts/labels.rst

@@ -633,7 +633,7 @@ also be valid expressions in the region DSL; creating a label ``"(tag 1)"`` will
 lead to confusion.
 
 Labels are stored with their associated expressions as key-value pairs in *label dictionaries*.
-Label dictionaries are then used to create a cable-cell along with the :ref:`morphology <co_morphology>`
+Label dictionaries are then used to create a cable-cell along with the :ref:`morphology <morph>`
 and a :ref:`decor <cablecell-decoration>`. The decorations can be painted or placed on
 the regions or locsets defined in the label dictionary by referring to their labels.
 

doc/python/cable_cell.rst

@@ -192,7 +192,7 @@ Cable cells
 
     .. note::
         The regions and locsets defined in the label dictionary are
-        :ref:`concretised <labels-concretise>` when the cable cell is constructed,
+        :ref:`thingified <labels-thingify>` when the cable cell is constructed,
         and an exception will be thrown if an invalid label expression is found.
 
         There are two reasons an expression might be invalid: