transientVector_ must be declared transient

This is a fix for a bugs in DataFormats/TauReco/src/classes_def_3.xml, which is fatal in our ROOT6 branch. ROOT 5 still works because it has looser checking for these things,
The data member "transientVector_" of the AssociationVector template is transient, but this dictionary fails to declare it as transient for some AssociationVector template instances.
This fix will fix a failure in 22 ROOT 6 relvals.