Clear up QWindow::isActive() documentation

The isActive function does not determine if a window should be active,
but whether it is currently active. The way the documentation was phrased
may have lead people to believe the former.

Pick-to: 6.2 6.2.0 5.15
Change-Id: I05a4cb3d8784a2fefa24bdd42ea96cfdae22b9d1
Reviewed-by: Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>

src/gui/kernel/qwindow.cpp

@@ -1241,11 +1241,13 @@ bool QWindow::isExposed() const
 */
 
 /*!
-    Returns \c true if the window should appear active from a style perspective.
+    Returns \c true if the window is active.
 
     This is the case for the window that has input focus as well as windows
     that are in the same parent / transient parent chain as the focus window.
 
+    Typically active windows should appear active from a style perspective.
+
     To get the window that currently has focus, use QGuiApplication::focusWindow().
 */
 bool QWindow::isActive() const