CPP: Move VirtualDispatch.qll into the controlflow directory (I don't see the point in having a subdirectory for one file, when we don't anticipate any other files ever being added there).

Author: geoffw0

cpp/ql/src/Security/CWE/CWE-457/InitializationFunctions.qll

@@ -4,7 +4,7 @@
 
 import cpp
 import external.ExternalArtifact
-private import semmle.code.cpp.dispatch.VirtualDispatch
+private import semmle.code.cpp.controlflow.VirtualDispatch
 import semmle.code.cpp.NestedFields
 import Microsoft.SAL
 import semmle.code.cpp.controlflow.Guards