[clang-tidy] Handle template instantiations in modenize-use-default check

Summary:
Duplicate fixes were being created for explicit template instantiations
of out-of-line constructors or destructors.

Fixes PR30921.

Reviewers: alexfh, aaron.ballman

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D26582

llvm-svn: 287091