BUG/MEDIUM: mux-quic: fix crash due to invalid trace arg

Traces argument were incorrectly used in qcs_free(). A qcs was specified
as first arg instead of a connection. This will lead to a crash if
developer qmux traces are activated. This is now fixed.

This bug has been introduced with QUIC MUX traces rework. No need to
backport.
1 file changed