Update docs/heuristics.rst for RF matching_parameters key

Co-authored-by: Yaroslav Halchenko <[email protected]>

Author: pvelasco

docs/heuristics.rst

@@ -133,9 +133,9 @@ The parameters that can be specified and the allowed options are defined in ``bi
   Example::
 
     POPULATE_INTENDED_FOR_OPTS = {
-            'matching_parameter': 'ImagingVolume',
+            'matching_parameters': ['ImagingVolume', 'Shims'],
             'criterion': 'Closest'
     }
 
 If ``POPULATE_INTENDED_FOR_OPTS`` is not present in the heuristic file, ``IntendedFor``
-will not be populated automatically.
+will not be populated automatically.