chore(colors): remove unecessary modeline

This modeline was used to allow syntax highlighting of Lua
in the `highlite.vim` file, but now that the file is a Lua file we don't
need to manually set the filetype.

colors/highlite.lua

@@ -972,4 +972,3 @@ require(vim.g.colors_name)(
 )
 
 -- Thanks to Romain Lafourcade (https://github.com/romainl) for the original template (romainl/vim-rnb).
--- vim: ft=lua