refactor: Remove utils.request shim

* This is no longer needed as people have probably moved on from 0.5

lua/symbols-outline/utils/lsp_utils.lua

@@ -1,37 +1,5 @@
-local vim = vim
-
 local M = {}
 
--- callback args changed in Neovim 0.5.1/0.6. See:
--- https://github.com/neovim/neovim/pull/15504
-local function mk_handler(fn)
-  return function(...)
-    local config_or_client_id = select(4, ...)
-    local is_new = type(config_or_client_id) ~= 'number'
-    if is_new then
-      fn(...)
-    else
-      local err = select(1, ...)
-      local method = select(2, ...)
-      local result = select(3, ...)
-      local client_id = select(4, ...)
-      local bufnr = select(5, ...)
-      local config = select(6, ...)
-      fn(
-        err,
-        result,
-        { method = method, client_id = client_id, bufnr = bufnr },
-        config
-      )
-    end
-  end
-end
-
--- from mfussenegger/nvim-lsp-compl@29a81f3
-function M.request(bufnr, method, params, handler)
-  return vim.lsp.buf_request(bufnr, method, params, mk_handler(handler))
-end
-
 function M.is_buf_attached_to_lsp(bufnr)
   local clients = vim.lsp.buf_get_clients(bufnr or 0)
   return clients ~= nil and #clients > 0