MINOR: quic: remove references to burst in quic-cc-algo parsing

MINOR: quic: remove references to burst in quic-cc-algo parsing

Pacing activation configuration has been recently revamped. Previously,
pacing related quic-cc-algo argument was used to specify a burst size.
It evolved into a boolean value as burst size is dynamically calculated
now. As such, removes any references to the old burst value in config
parsing code for cleaner code.

This should be backported up to 3.1, after a period of observation.