MSW tests build fix: forgotten part of a previous commit

Add missing function declaration. This should have been part of a963edc.

tests/config/regconf.cpp

@@ -39,6 +39,7 @@ private:
     CPPUNIT_TEST_SUITE_END();
 
     void ReadWrite();
+    void DeleteRegistryKeyFromRedirectedView();
 
     wxDECLARE_NO_COPY_CLASS(RegConfigTestCase);
 };