nvim: plugins: Drop vim-coq-plugin

coqtail can provide syntax highlighting. Not sure why we ever
added vim-coq-plugin.

nvim/.config/nvim/after/plugin/coqtail.vim

@@ -1,2 +0,0 @@
-let g:coqtail_nosyntax         = 1
-let g:coqtail_noindent_comment = 1

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

@@ -74,10 +74,7 @@ local init = function ()
   use 'mfussenegger/nvim-lint'
   use 'simrat39/rust-tools.nvim'
   -- Coq
-  use {
-    'whonore/Coqtail',
-    'jlapolla/vim-coq-plugin'
-  }
+  use 'whonore/Coqtail'
   -- treesitter based syntax highlighting
   use {
     'nvim-treesitter/nvim-treesitter',