Fix a regression in the source locations for unary trait expressions.

I tried to use an assert to prove that I could remove each of the
arguments I did, but ended up writing my assert with inverted logic.
Doh! Reported by Xi Wang on cfe-dev. I have manually verified the source
locations and ranges for these using -ast-dump. I tried writing a test
case that would catch these, but these expressions aren't exposed in the
c-index-test's token annotation utility.

llvm-svn: 132284