Fix a couple typos in assertion messages.
Fix a couple typos in assertion messages.


Former-commit-id: 5bf686da795311ac342768e914909e8f7e0619db
darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,darkbuck/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide,Trass3r/Halide,darkbuck/Halide,Trass3r/Halide