kcm/colors: don't dull accent colour on dark themes in colorsapplicator

User demand shows that bright accent colours are wanted over potentially
better legibility, so let's avoid changing them.

BUG: 442820
FIXED-IN: 5.25

kcms/colors/colorsapplicator.h

@@ -43,13 +43,7 @@ inline QColor alphaBlend(const QColor &foreground, const QColor &background)
 inline QColor accentBackground(const QColor &accent, const QColor &background)
 {
     auto c = accent;
-    // light bg
-    if (KColorUtils::luma(background) > 0.5) {
-        c.setAlphaF(0.7);
-    } else {
-        // dark bg
-        c.setAlphaF(0.4);
-    }
+    c.setAlphaF(0.7);
     return alphaBlend(c, background);
 }