Update strings of already created wxGridCellChoiceEditor too

Calling wxGridCellChoiceEditor::SetParameters() didn't have any effect
if the editor had been already used because this method only updated the
internally stored m_choices, used for creating the combobox, but not the
strings actually used by the combobox, if it had been already created.

Also mention that this works in the documentation.

Closes #10465.

interface/wx/grid.h

@@ -693,7 +693,11 @@ public:
                            bool allowOthers = false);
 
     /**
-        Parameters string format is "item1[,item2[...,itemN]]"
+        Parameters string format is "item1[,item2[...,itemN]]".
+
+        This method can be called before the editor is used for the first time,
+        or later, in which case it replaces the previously specified strings
+        with the new ones.
     */
     virtual void SetParameters(const wxString& params);
 };