CLEANUP: quic,ssl: fix tiny typos in C comments

This fixes 4 tiny and harmless typos in mux_quic.c, quic_tls.c and
ssl_sock.c. Originally sent via GitHub PR #1843.

Signed-off-by: cui fliter <imcusg@gmail.com>
[Tim: Rephrased the commit message]
[wt: further complete the commit message]
3 files changed