golden layout panes in the initial microsynteny view should be individually dismissable (at least the legends)

[adf-ncgr]

I'm not entirely sure if this is a regression, but I think we used to be able to close at least the legend panes (using the "X" that would appear to the right of their pane header tab, as still appears in panes sprouted later like the macrosynteny view and dotplots). Maybe this was a conscious decision since there's no way to recall them other than reloading? Not a major problem, but just noticed that I couldn't dismiss the macrosynteny legend, which seemed a bit superfluous since I wasn't viewing macrosynteny.