[Haskell-cafe] Vim syntax file typo

Hello Haskell Cafe, The attached patch fixes what looks to be a typo in a comment in the Haskell Vim syntax file. Pretty trivial, but I'm mailing it to this list as it's listed as the maintainer of the file and I believe that's the Vim policy. Please let me know if there's somewhere more appropriate I should send this or if you'd prefer me to just submit it as a pull request on the Vim Github. Thanks, Matt