Issue 10938 - ICE on recursive instantiation in opDispatch 

https://d.puremagic.com/issues/show_bug.cgi?id=10938

By fixing issue 10736 (314a1cca9ff56775b9e2a9cf81564135be0726b1), all of template instance semantic are reliably finished by the deferred mechanism.
And it had removed the necessity of the code in `DotTemplateInstanceExp::semanticY` for the issue 4003.

Therefore, just remove the unnecessary code to fix the ICE.