Remove legacy hack forcing justfile to be handled as Makefiles

Both VIM and Neovim ship with native ftdetect rules to detect justfiles
and proper syntax highlighting for them. This modline hack is absolete
and actually makes these files *less* accessible in modern editors.

Author: alerque

README.md

@@ -517,8 +517,11 @@ 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`:
+For older versions of VIM/Neovim before Justfile syntax support was added and
+when vim-just cannot be installed, it is possible to use the *make* filetype
+as a substitute. 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")
@@ -537,6 +540,9 @@ per-file basis:
 # vim: set ft=make :
 ```
 
+Note that forcing this workaround in the modeline will make it *harder* for
+people to use that have up to date editors with proper Justfile support.
+
 ### Emacs
 
 [just-mode](https://github.com/leon-barrett/just-mode.el) provides syntax

justfile

@@ -233,4 +233,3 @@ test-release-workflow:
 # Local Variables:
 # mode: makefile
 # End:
-# vim: set ft=make :