fix comment claiming ParseConnectionID reuses the data slice

[sukunrt]

This is protocol.ParseConnectionID. It copies data from b.

func ParseConnectionID(b []byte) ConnectionID {
	if len(b) > maxConnectionIDLen {
		panic("invalid conn id length")
	}
	var c ConnectionID
	c.l = uint8(len(b))
	copy(c.b[:c.l], b)
	return c
}

Feel free to close if this is too small etc. Apologies if this is just plain mistaken.

[codecov]

Codecov Report

Merging #3848 (2b4d964) into master (da198b7) will increase coverage by 0.01%.
The diff coverage is 70.21%.

@@            Coverage Diff             @@
##           master    #3848      +/-   ##
==========================================
+ Coverage   83.92%   83.94%   +0.01%     
==========================================
  Files         142      146       +4     
  Lines       14208    14307      +99     
==========================================
+ Hits        11924    12009      +85     
- Misses       1850     1858       +8     
- Partials      434      440       +6     

Impacted Files	Coverage Δ
internal/wire/header.go	82.23% <ø> (ø)
quicvarint/varint.go	76.47% <ø> (+9.23%)	⬆️
sys_conn_helper_nonlinux.go	50.00% <50.00%> (ø)
sys_conn_buffers_write.go	57.78% <57.78%> (ø)
sys_conn_buffers.go	64.44% <64.44%> (ø)
transport.go	62.45% <72.73%> (-2.08%)	⬇️
sys_conn_helper_linux.go	81.25% <81.25%> (ø)
sys_conn_oob.go	73.68% <100.00%> (+4.57%)	⬆️
sys_conn_windows.go	100.00% <100.00%> (+27.27%)	⬆️

... and 1 file with indirect coverage changes

[marten-seemann]

Thank you! That's correct. Must have missed to update the comment in #3529.