nvim: plugins: Drop rainbow

Does not really work with treesitter.

There is nvim-ts-rainbow but it seems to have performance problems.
https://github.com/p00f/nvim-ts-rainbow/issues/5

nvim/.config/nvim/after/ftplugin/markdown.vim

@@ -13,7 +13,3 @@ let g:pandoc#formatting#textwidth           = 79
 let g:pandoc#formatting#mode                = "hA"
 let g:pandoc#completion#bib#mode            = 'citeproc'
 let g:pandoc#syntax#codeblocks#embeds#langs = ["c", "rust", "haskell", "literatehaskell=lhaskell", "bash=sh"]
-
-" Rainbow Parentheses affects syntax highlighting for URL links. Turn it off
-" for markdown files.
-autocmd! BufEnter <buffer> RainbowToggleOff

nvim/.config/nvim/init.lua

@@ -87,8 +87,6 @@ vim.g.vimtex_view_general_viewer  = 'zathura'
 vim.g.vimtex_view_general_options = '--unique \\@pdf\\#src:@tex:@line:@col'
 -- Needs to be before togglelist gets loadded
 vim.g.toggle_list_no_mappings     = 1
--- Enable rainbow brackets everywhere
-vim.g.rainbow_active              = 1
 -- Needs to be set before nvim-peekup
 vim.g.peekup_paste_before         = '<Leader>P'
 vim.g.peekup_paste_after          = '<Leader>p'

nvim/.config/nvim/lua/plugins.lua

@@ -48,8 +48,6 @@ local init = function ()
   use 'sindrets/diffview.nvim'
   -- Boost vim command line mode
   use 'vim-utils/vim-husk'
-  -- Rainbow Parentheses
-  use 'luochen1990/rainbow'
   -- Formatting
   use {
     'sbdchd/neoformat',