[mlir][python] Disable pytype not-yet-supported error on Buffer import (#189440)

For pyhon versions <3.12, pytype complains that:

```
error: in <module>: collections.abc.Buffer not supported yet [not-supported-yet]
  from collections.abc import Buffer as _Buffer
```

Since it seems like this code intends to support <3.12, disabling the
type error on this line.

mlir/tools/mlir-tblgen/OpPythonBindingGen.cpp

@@ -49,7 +49,7 @@ import builtins
 from typing import Any as _Any, Sequence as _Sequence, Union as _Union, Optional as _Optional
 import sys as _sys
 if _sys.version_info >= (3, 12):
-  from collections.abc import Buffer as _Buffer
+  from collections.abc import Buffer as _Buffer  # pytype: disable=not-supported-yet
 else:
   try:
     from typing_extensions import Buffer as _Buffer