Autotest: Fix build error with QT_NO_EXCEPTIONS

The function declaration has to be in the same ifdefs as the
implementation.

Change-Id: I78c5795baef4adba7439f66252819963db164759
Reviewed-by: Oliver Wolff <oliver.wolff@theqtcompany.com>

tests/auto/corelib/thread/qfuture/tst_qfuture.cpp

@@ -1438,6 +1438,8 @@ void tst_QFuture::nestedExceptions()
     QVERIFY(MyClass::caught);
 }
 
+#endif // QT_NO_EXCEPTIONS
+
 void tst_QFuture::nonGlobalThreadPool()
 {
     static Q_CONSTEXPR int Answer = 42;
@@ -1485,7 +1487,5 @@ void tst_QFuture::nonGlobalThreadPool()
     }
 }
 
-#endif // QT_NO_EXCEPTIONS
-
 QTEST_MAIN(tst_QFuture)
 #include "tst_qfuture.moc"