Release buffer

[radarhere]

Sequel to #6974, addressing #6974 (comment)

I think this is missing a call to PyBuffer_Release().

This makes sense, as per https://docs.python.org/3/c-api/buffer.html

There are two ways for a consumer of the buffer interface to acquire a buffer over a target object:

• call PyObject_GetBuffer() with the right parameters;
• call PyArg_ParseTuple() (or one of its siblings) with one of the y*, w* or s* format codes.

In both cases, PyBuffer_Release() must be called when the buffer isn’t needed anymore. Failure to do so could lead to various issues such as resource leaks.