Make \brief of Saving a Game to File actually brief

Specifically, prune it to fit on a single line.
Much of what it was saying was implicit in its context already.
It also neglected to mention CBOR's part in the story.

Pick-to: 6.6 6.5
Task-number: QTBUG-111228
Change-Id: I161a345cbbea8b706490fcbbadecd01b8946af31
Reviewed-by: Konrad Kujawa <konrad.kujawa@qt.io>
Reviewed-by: Paul Wicking <paul.wicking@qt.io>

examples/corelib/serialization/savegame/doc/src/savegame.qdoc

@@ -6,8 +6,7 @@
     \examplecategory {Data Processing & I/O}
     \title JSON Save Game Example
 
-    \brief The JSON Save Game example demonstrates how to save and load a
-    small game using QJsonDocument, QJsonObject and QJsonArray.
+    \brief How to save and load a game using Qt's JSON or CBOR classes.
 
     Many games provide save functionality, so that the player's progress through
     the game can be saved and loaded at a later time. The process of saving a