Drop documentatino of obsolete workaround for lack of VIM support

Both VIM and Neovim have shipped with native support and for several
releases. This obsolete work around just confuses the issue.

Author: alerque

README.md

@@ -515,28 +515,6 @@ git clone https://github.com/NoahTheDuke/vim-just.git
 [Nvim Treesitter](https://github.com/nvim-treesitter/nvim-treesitter) plugin
 for Neovim.
 
-#### Makefile Syntax Highlighting
-
-Vim's built-in makefile syntax highlighting isn't perfect for `justfile`s, but
-it's better than nothing. You can put the following in `~/.vim/filetype.vim`:
-
-```vimscript
-if exists("did_load_filetypes")
-  finish
-endif
-
-augroup filetypedetect
-  au BufNewFile,BufRead justfile setf make
-augroup END
-```
-
-Or add the following to an individual `justfile` to enable `make` mode on a
-per-file basis:
-
-```text
-# vim: set ft=make :
-```
-
 ### Emacs
 
 [just-mode](https://github.com/leon-barrett/just-mode.el) provides syntax