Motivation for this change

I'm using this plugin, and I keep getting the following error at Vim startup

Error detected while processing /nix/store/37njws9gkfz3w5q1mm9kf3fcbd58lwqs-vimplugin-vim-terraform-2019-12-16/share/vim-plugins/vim-terraform/ftdetect/terraform.vim:                                                                                                           
line    2:                                                                                                                                                                                                                                                                       
E216: No such group or event: filetypedetect BufRead,BufNewFile *.tf

This issue used to block Vim's manifest generation, but that got fixed in #66536. That fix was a workaround though, this should fix that as well as Vim's startup.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

Notify maintainers

cc @