Fix a typo in the comment. (#2866)
Fix a typo in the comment. (#2866)

I was trying to run this test and I had copied the name of the function
from the comment, and it took a good while to figure out why
`go test -run` was returning `testing: warning: no tests to run`.
grpc/grpc-go,stanley-cheung/grpc-go,grpc/grpc-go,menghanl/grpc-go,dfawley/grpc-go,stanley-cheung/grpc-go,dfawley/grpc-go,menghanl/grpc-go