Remove .virtualenv from Haskell.gitignore

The file name was incorrect, so it was having no effect. Also, the sandbox environment that this was supposed to be ignoring is deprecated. Probably best to just drop it entirely.

Haskell.gitignore

@@ -6,7 +6,6 @@ cabal-dev
 *.chs.h
 *.dyn_o
 *.dyn_hi
-.virthualenv
 .hpc
 .hsenv
 .cabal-sandbox/