Remove vim-go

It's too heavy and it also seems to have some issues. Gophers that use Go can manually install it

Fixed https://github.com/amix/vimrc/issues/537

update_plugins.py

@@ -45,7 +45,6 @@ goyo.vim https://github.com/junegunn/goyo.vim
 vim-zenroom2 https://github.com/amix/vim-zenroom2
 vim-repeat https://github.com/tpope/vim-repeat
 vim-commentary https://github.com/tpope/vim-commentary
-vim-go https://github.com/fatih/vim-go
 vim-gitgutter https://github.com/airblade/vim-gitgutter
 gruvbox https://github.com/morhetz/gruvbox
 vim-flake8 https://github.com/nvie/vim-flake8