wxGUI: fix https://trac.osgeo.org/grass/ticket/1602 in GCPmanager

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@51078 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/gcp/toolbars.py

@@ -86,8 +86,7 @@ class GCPDisplayToolbar(BaseToolbar):
         # add tool to toggle active map window
         self.togglemapid = wx.NewId()
         self.togglemap = wx.Choice(parent = self, id = self.togglemapid,
-                                   choices = [_('source'), _('target')],
-                                   style = wx.CB_READONLY)
+                                   choices = [_('source'), _('target')])
 
         self.InsertControl(10, self.togglemap)