Doc: Minor QDialog clarification

Minor rewrite of a bit that caused some confusion.

Fixes: QTBUG-73335
Change-Id: Ic1df44e62a29035c7b93052204fbe9ef72db5f40
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>

src/widgets/dialogs/qdialog.cpp

@@ -263,12 +263,11 @@ void QDialogPrivate::deletePlatformHelper()
 
     The most common way to display a modal dialog is to call its
     exec() function. When the user closes the dialog, exec() will
-    provide a useful \l{#return}{return value}. Typically,
-    to get the dialog to close and return the appropriate value, we
-    connect a default button, e.g. \uicontrol OK, to the accept() slot and a
-    \uicontrol Cancel button to the reject() slot.
-    Alternatively you can call the done() slot with \c Accepted or
-    \c Rejected.
+    provide a useful \l{#return}{return value}. To close the dialog
+    and return the appropriate value, you must connect a default button,
+    e.g. an \uicontrol OK button to the accept() slot and a
+    \uicontrol Cancel button to the reject() slot. Alternatively, you
+    can call the done() slot with \c Accepted or \c Rejected.
 
     An alternative is to call setModal(true) or setWindowModality(),
     then show(). Unlike exec(), show() returns control to the caller