[ASTMatchers] Add templateTypeParmDecl() to Registry.cpp

Summary:
This appears to have been forgotten when templateTypeParmDecl() was initially
added.

Reviewers: alexfh, aaron.ballman

Subscribers: aaron.ballman, klimek, aemerson, rengolin, samparker, cfe-commits

Differential Revision: https://reviews.llvm.org/D23448

llvm-svn: 278507