Doc/QCheckBox: remove outdated paragraph

Remove an outdated paragraph which mentions some 'important inherited
functions' - the list is outdated and therefore wrong, and no other class
has such a paragraph.

Fixes: QTBUG-130916
Change-Id: Ia1d98da35564d542ca2758070cc1d5b5525b6faf
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 423496dcfbcd3a779653a4186a3b49ef8b5d2d7f)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/widgets/widgets/qcheckbox.cpp

@@ -80,12 +80,6 @@ public:
     {QShortcut} documentation for details. To display an actual ampersand,
     use '&&'.
 
-    Important inherited functions: text(), setText(), text(), pixmap(),
-    setPixmap(), accel(), setAccel(), isToggleButton(), setDown(), isDown(),
-    isOn(), checkState(), autoRepeat(), isExclusiveToggle(), group(),
-    setAutoRepeat(), toggle(), pressed(), released(), clicked(), toggled(),
-    checkState(), and checkStateChanged().
-
     \sa QAbstractButton, QRadioButton
 */