Fix #81302: Stream position after stream filter removed

When flushing the stream filters actually causes data to be written to
the stream, we need to update its position, because that is

Fix #81302: Stream position after stream filter removed

When flushing the stream filters actually causes data to be written to
the stream, we need to update its position, because that is not done by
the streams' write methods.

Closes GH-7354.

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