Suppress byte-compile warning

[syohex]

' should be used rather than #' in make-obsolete and #' causes byte-compile warning. You can get following warning by following steps.

1. byte-compile haskell.el
2. load haskell.elc
3. byte-compile haskell.el

haskell.el:67:2:Warning: `haskell-process-completions-at-point' is an obsolete
    function (as of June 19, 2015); use
    `haskell-completions-sync-completions-at-point' instead.

[gracjan]

Nice catch. Thanks.