fix(buffer_previewer): no preview showing when set nomodifiable (#3077

)

Not showing a preview with the new changes in the latest changes of
[plenary.nvim PR
#575](nvim-lua/plenary.nvim#575).

The error occurs when changing from `nomodifiable` to `modifiable`.
Telescope itself works, but the previews don't render.

(cherry picked from commit 1084d07)

lua/telescope/previewers/buffer_previewer.lua

@@ -368,6 +368,7 @@ previewers.new_buffer_previewer = function(opts)
  else
  local bufnr = vim.api.nvim_create_buf(false, true)
  set_bufnr(self, bufnr)
+ vim.api.nvim_buf_set_option(bufnr, "modifiable", true)
 
  vim.schedule(function()
  if vim.api.nvim_buf_is_valid(bufnr) then