Remove special lambda unicode character, it didn't work anyway

Remove special lambda unicode character, it didn't work anyway
Since lambda is a lower-case letter, it's debatable whether we want to
steal it to mean lambda in Haskell source.  However if we did, then we
would probably want to make it a "special" symbol, not just a reserved
symbol, otherwise writing \x->... (using unicode characters of course)
wouldn't work, because \x would be treated as a single identifier,
you'd need a space.