minimal-display-settings might become too large, scroll is needed to permit resizing

I noticed and prepared a fix of the following issue: with many Display Profiles (as happen with various rotation combinations of different screens (e.g. a yoga laptop not always in the same position plus monitors in various positions and orientations), the minimal-display-setting dialog become in some circumstances too wide and can't be resized to select the desired Display Profile.

I prepared mar-xfce-settings.patch UI-only change with glade 3.38.2, with the following steps:

• select GtkViewport: "Add Parent" -> "Scrolled Window"

than select the added GtkScrolledWindow:

1. uncheck "Overlay Scrolling" (to make scroll bar well visible)
2. change "Top Left" -> "Bottom Left" (to have scroll bar on top so everything else is on the Bottom)
3. Vertical Scroll Bar policy change "Automatic" -> "Never" (only horizontal scrolling can be too large)

Here the glade relevant portion:

And an example of result (not a moment where Profiles were too many as instead can occur):