Meaningless test simplification in the sorry spec tests.

Meaningless in the sense that it still doesn't fix the "what the heck is
happening" invalid buffer ID tests on nightly's semantic token
highlighting.

spec/helpers.lua

@@ -160,13 +160,12 @@ end
 
 ---Wait a few seconds for line diagnostics, erroring if none arrive.
 function helpers.wait_for_line_diagnostics()
+  local params = vim.lsp.util.make_position_params(0, 'utf-16')
   local succeeded, _ = vim.wait(15000, function()
-    if progress.at(vim.lsp.util.make_position_params()) == progress.Kind.processing then
+    if progress.at(params) == progress.Kind.processing then
       return false
     end
-    local diagnostics = util.lean_lsp_diagnostics {
-      lnum = vim.api.nvim_win_get_cursor(0)[1] - 1,
-    }
+    local diagnostics = util.lean_lsp_diagnostics { lnum = params.position.line }
     return #diagnostics > 0
   end)
   assert.message('Waited for line diagnostics but none came.').True(succeeded)