Utils::DetailsButton: Don't make button vertically expanding

Change default vertical size policy of the DetailsButton from
Expanding to Preferred: This way it won't be 'greedy' and enlarge
just because there is space left.

src/libs/utils/detailsbutton.cpp

@@ -74,7 +74,7 @@ void FadingPanel::fadeTo(float value)
 DetailsButton::DetailsButton(QWidget *parent) : QAbstractButton(parent), m_fader(0)
 {
     setCheckable(true);
-    setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Expanding);
+    setSizePolicy(QSizePolicy::Fixed, QSizePolicy::Preferred);
     setText(tr("Details"));
 }