Don't eagerly typo-correct to a keyword if the next token is a right paren.

Take advantage of the delayed typo no longer being eagerly corrected to
a keyword to filter out keyword corrections (and other things like
unresolved & overloaded expressions, which have placeholder types) when
correcting typos inside of a decltype().

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@234623 91177308-0d34-0410-b5e6-96231b3b80d8