Remove useless lines not required with vim-plug
Remove useless lines not required with vim-plug

See https://github.com/junegunn/vim-plug/wiki/faq#migrating-from-other-
plugin-managers

tdfirth/haskell-vim-now,pavlosgi/haskell-vim-now,ideruga/haskell-vim-now,begriffs/haskell-vim-now,everyevery/haskell-vim-now