QDuplicateTracker: port reserve() from int to qsizetype

Was missed in the int -> qsizetype port for Qt 6.0.

Pick-to: 6.2 6.1
Change-Id: I1ae8190601f2e1a1bc02a736c12230a9c71acb18
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/tools/qduplicatetracker_p.h

@@ -106,7 +106,7 @@ class QDuplicateTracker {
     Q_DISABLE_COPY_MOVE(QDuplicateTracker);
 public:
     QDuplicateTracker() = default;
-    void reserve(int n) { set.reserve(n); }
+    void reserve(qsizetype n) { set.reserve(n); }
     [[nodiscard]] bool hasSeen(const T &s)
     {
         return !set.insert(s).second;