Fusion: desaturate the brown shades

The reference images in tst_qframe had to be updated to match the palette.

[ChangeLog][QtWidgets][QFusionStyle] The default palette used by the
platform agnostic Fusion style has been desaturated. Previously the window
background color, and other colors derived from it, were brown shades. Now
these colors are neutral gray that fit better on any desktop.

Change-Id: Id6a05e05563b8cbc8f378ee415a64b8f99012b60
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>

src/gui/kernel/qpalette.cpp

@@ -1115,14 +1115,14 @@ void QPalette::setColorGroup(ColorGroup cg, const QBrush &foreground, const QBru
 
 Q_GUI_EXPORT QPalette qt_fusionPalette()
 {
-    QColor backGround(239, 235, 231);
+    QColor backGround(239, 239, 239);
     QColor light = backGround.lighter(150);
     QColor mid(backGround.darker(130));
     QColor midLight = mid.lighter(110);
     QColor base = Qt::white;
     QColor disabledBase(backGround);
     QColor dark = backGround.darker(150);
-    QColor darkDisabled = QColor(209, 200, 191).darker(110);
+    QColor darkDisabled = QColor(209, 209, 209).darker(110);
     QColor text = Qt::black;
     QColor hightlightedText = Qt::white;
     QColor disabledText = QColor(190, 190, 190);
@@ -1145,7 +1145,7 @@ Q_GUI_EXPORT QPalette qt_fusionPalette()
 
     fusionPalette.setBrush(QPalette::Active, QPalette::Highlight, QColor(48, 140, 198));
     fusionPalette.setBrush(QPalette::Inactive, QPalette::Highlight, QColor(48, 140, 198));
-    fusionPalette.setBrush(QPalette::Disabled, QPalette::Highlight, QColor(145, 141, 126));
+    fusionPalette.setBrush(QPalette::Disabled, QPalette::Highlight, QColor(145, 145, 145));
     return fusionPalette;
 }