neovim: Drop fcitx-vim

This was significantly increasing start time and I didn't use it too
much. There should be lighter alternatives out there that aren't
packaged in nixpkgs.

home/neovim.nix

@@ -476,7 +476,6 @@ in
       neoformat
       vim-crystal
       vim-nix
-      fcitx-vim
       tagbar
       rainbow-delimiters-nvim
     ];