Let QAccessibleButton::text return something even when not visible.

Buttons would not report their text when hidden, which is inconsistent.
Reviewed-by: Jan-Arve
(cherry picked from commit 1897ca20a343121422b354a7910814ddd37abd17)

src/plugins/accessible/widgets/simplewidgets.cpp

@@ -155,9 +155,6 @@ bool QAccessibleButton::doAction(int action, int child, const QVariantList &para
 QString QAccessibleButton::text(Text t, int child) const
 {
     QString str;
-    if (!widget()->isVisible())
-        return str;
-
     switch (t) {
     case Accelerator:
         {