[analyzer] Remove bogus assert: in C++11, 'new' can do list-initialization.

Previously, we asserted that whenever 'new' did not include a constructor
call, the type must be a non-record type. In C++11, however, uniform
initialization syntax (braces) allow 'new' to construct records with
list-initialization: "new Point{1, 2}".

Removing this assertion should be perfectly safe; the code here matches
what VisitDeclStmt does for regions allocated on the stack.

<rdar://problem/14403437>