Fix GRID3d_AGGREGATE_MAP parameter documentation

The example given for documentation used the `CONFIG_AGGMAP`
argument while the forward describes that it takes
`CONFIG_AGGREGATE` the argument.

src/xtgeoapp_grd3dmaps/aggregate/grid3d_aggregate_map.py

@@ -32,7 +32,7 @@
 EXAMPLES = """
 .. code-block:: console
 
-  FORWARD_MODEL GRID3D_AGGREGATE_MAP(<CONFIG_AGGMAP>=conf.yml, <ECLROOT>=<ECLBASE>)
+  FORWARD_MODEL GRID3D_AGGREGATE_MAP(<CONFIG_AGGREGATE>=conf.yml, <ECLROOT>=<ECLBASE>)
 """