Documentation cleanup: eliminated Doxygen warnings by deleting a doc comment

on ASTContext::CreateTypeSourceInfo that duplicated information from the
(more complete) version in ASTContext.h.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158504 91177308-0d34-0410-b5e6-96231b3b80d8