SilverSearcher: Fix release build

Change-Id: Ib55304708454204f14fe3429f02108678f7a3e9e
Reviewed-by: Przemyslaw Gorszkowski <pgorszkowski@gmail.com>

src/plugins/silversearcher/silversearcherplugin.cpp

@@ -44,10 +44,11 @@ void SilverSearcherPlugin::extensionsInitialized()
 {
 }
 
+#ifdef WITH_TESTS
 QList<QObject *> SilverSearcherPlugin::createTestObjects() const
 {
     return {new OutputParserTest};
 }
-
+#endif
 } // namespace Internal
 } // namespace SilverSearcher