AutoTest: Remove old declaration

Missed while transition to QC 4.0.

Change-Id: Ib62b52b607d8f7e929c482622f48804c01a25a24
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/autotest/autotestplugin.h

@@ -73,7 +73,6 @@ public:
     static void clearChoiceCache();
 
 private:
-    bool checkLicense();
     void initializeMenuEntries();
     void onRunAllTriggered();
     void onRunSelectedTriggered();