Remove color from discard dialog text, since it uses system style

Originally a lot of text would not be readable when in dark theme
because the text would be light, but the background would always be
white.

resources/qml/Dialogs/DiscardOrKeepProfileChangesDialog.qml

@@ -100,7 +100,6 @@ UM.Dialog
                 {
                     text: styleData.value
                     font: UM.Theme.getFont("system")
-                    color: UM.Theme.getColor("setting_control_disabled_text")
                 }
             }