fix(diagnostic): set effective buffer number in autocmd (again) (#16589)

Follow up to #16474.

runtime/lua/vim/diagnostic.lua

@@ -1344,12 +1344,14 @@ function M.reset(namespace, bufnr)
     end
   end
 
-  vim.api.nvim_command(
-    string.format(
-      "doautocmd <nomodeline> DiagnosticChanged %s",
-      vim.fn.fnameescape(vim.api.nvim_buf_get_name(bufnr))
+  vim.api.nvim_buf_call(bufnr, function()
+    vim.api.nvim_command(
+      string.format(
+        "doautocmd <nomodeline> DiagnosticChanged %s",
+        vim.fn.fnameescape(vim.api.nvim_buf_get_name(bufnr))
+      )
     )
-  )
+  end)
 end
 
 --- Add all diagnostics to the quickfix list.