ConfigDialog: fix some gray mismatch in prev commit (#4797)

Remove gray underline on text items (font size items).
Adjust gray color of ButtonProgressWidget to match the
one of ToggleSwitch (just need to invert it, as it's
used to select button, which cause this color to be
inverted).

frontend/ui/widget/buttonprogresswidget.lua

@@ -75,7 +75,9 @@ function ButtonProgressWidget:update()
         if self.thin_grey_style then
             button.frame.color = Blitbuffer.COLOR_DARK_GRAY -- no black border around gray squares
             if highlighted then
-                button.frame.background = Blitbuffer.COLOR_DARK_GRAY
+                -- The button and its frame background will be inverted,
+                -- so invert the color we want so it gets inverted back
+                button.frame.background = Blitbuffer.COLOR_DARK_GRAY:invert()
                 button = FrameContainer:new{ -- add margin back
                     margin = button_margin,
                     padding = 0,

frontend/ui/widget/configdialog.lua

@@ -391,7 +391,7 @@ function ConfigOption:init()
                             underline_padding = padding_button,
                             padding_left = d > 1 and horizontal_half_padding,
                             padding_right = d < #self.options[c].item_text and horizontal_half_padding,
-                            color = d == current_item and enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY or Blitbuffer.COLOR_WHITE,
+                            color = d == current_item and (enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY) or Blitbuffer.COLOR_WHITE,
                             enabled = enabled,
                         }
                     else
@@ -410,7 +410,7 @@ function ConfigOption:init()
                             underline_padding = -padding_button,
                             padding_left = d > 1 and horizontal_half_padding,
                             padding_right = d < #self.options[c].item_text and horizontal_half_padding,
-                            color = d == current_item and enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY or Blitbuffer.COLOR_WHITE,
+                            color = d == current_item and (enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY) or Blitbuffer.COLOR_WHITE,
                             enabled = enabled,
                         }
                     end
@@ -448,7 +448,7 @@ function ConfigOption:init()
                         underline_padding = -padding_button,
                         padding_left = d > 1 and horizontal_half_padding,
                         padding_right = d < #self.options[c].item_icons and horizontal_half_padding,
-                        color = d == current_item and enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY or Blitbuffer.COLOR_WHITE,
+                        color = d == current_item and (enabled and Blitbuffer.COLOR_BLACK or Blitbuffer.COLOR_DARK_GRAY) or Blitbuffer.COLOR_WHITE,
                         enabled = enabled,
                     }
                     option_items[d] = option_item