Update colab to TPUv2.

PiperOrigin-RevId: 628160440

Author: MarkDaoust

site/en/guide/tpu.ipynb

@@ -589,7 +589,9 @@
     "accelerator": "TPU",
     "colab": {
       "name": "tpu.ipynb",
-      "toc_visible": true
+      "toc_visible": true,
+      "machine_shape": "hm",
+      "gpuType": "V28"
     },
     "kernelspec": {
       "display_name": "Python 3",

tools/tensorflow_docs/tools/nblint/style/tensorflow.py

@@ -81,9 +81,7 @@ def not_translation(args):
 
 # Button checks
 
-# Look for class="tfo-notebook-buttons" (CSS used on website versions) or the
-# run-in-colab logo (for notebooks that stick to GitHub/Colab).
-is_button_cell_re = re.compile(r"class.*tfo-notebook-buttons|colab_logo_32px\.png")
+is_button_cell_re = re.compile(r"class.*tfo-notebook-buttons")
 
 
 def get_arg_or_fail(user_args, arg_name, arg_fmt):