Fixed setting property label with wxPGproperty::SetLabel

If there is a corresponding cell containing a cached text for column 0 then this text also needs to be updated when the label is changed.

See #16982.

include/wx/propgrid/property.h

@@ -2128,7 +2128,7 @@ public:
         m_helpString = helpString;
     }
 
-    void SetLabel( const wxString& label ) { m_label = label; }
+    void SetLabel( const wxString& label );
 
     void SetName( const wxString& newName );