[PATCH] CLEANUP: fix a typo found in the stream subsystem

[Joseph Herlant]

Hi,

This typo is in a code comment so not end-user visible.

The patch is attached, but if you want to view the diff online, you
can check: https://github.com/haproxy/haproxy/compare/master...aerostitch:ceanup_stream_typo

Thanks,
Joseph