QCache: fix accidental pessimization

By unconditionally removing the existing entry we never
hit the if (result.initialized) branch. Change it to
only remove the existing entry if we don't plan on inserting.

Task-number: QTBUG-88183
Change-Id: If4e7ebac23aa63d4b9d4b0a22882dd7d90a58e8b
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
(cherry picked from commit f08492c6fd9818c7d80b1725355453e179b4d85b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/corelib/tools/qcache.h

@@ -236,10 +236,9 @@ public:
 
     bool insert(const Key &key, T *object, qsizetype cost = 1)
     {
-        remove(key);
-
         if (cost > mx) {
             delete object;
+            remove(key);
             return false;
         }
         trim(mx - cost);