remove incorrect logging for client side retry packet

[VinozzZ]

Currently, when receiving a Retry packet from server, the client would log the retry packet as if it's part of its sending packet.

2021/03/05 09:51:31 client -> Sending packet 0 (1252 bytes) for connection 9d186471c610d30fef01, Initial
2021/03/05 09:51:31 client 	Long Header{Type: Initial, DestConnectionID: 9d186471c610d30fef01, SrcConnectionID: (empty), Token: (empty), PacketNumber: 0, PacketNumberLen: 2, Length: 1232, Version: TLS dev version (WIP)}
2021/03/05 09:51:31 client 	-> &wire.CryptoFrame{Offset: 0, Data length: 288, Offset + Data length: 288}
2021/03/05 09:51:31 client 	Long Header{Type: Retry, DestConnectionID: (empty), SrcConnectionID: b778d7e8, Token: 0xd530867e323c094c94c5dfcfe17631efcf7764183bea50ebb4f724fe99d0e7f2e8dcf61156484a91b453a7427e9bcebfca8968a2fc30ff58db34e3b7570d98a54859688a7f435f330882c5d09eab7d102c3d0d8dd2c0d376281378cfaf61f6600f06f5a6, Version: TLS dev version (WIP)}
2021/03/05 09:51:31 client <- Received Retry:
2021/03/05 09:51:31 client 	Long Header{Type: Retry, DestConnectionID: (empty), SrcConnectionID: b778d7e8, Token: 0xd530867e323c094c94c5dfcfe17631efcf7764183bea50ebb4f724fe99d0e7f2e8dcf61156484a91b453a7427e9bcebfca8968a2fc30ff58db34e3b7570d98a54859688a7f435f330882c5d09eab7d102c3d0d8dd2c0d376281378cfaf61f6600f06f5a6, Version: TLS dev version (WIP)}
2021/03/05 09:51:31 client Switching destination connection ID to: b778d7e8
2021/03/05 09:51:31 client 	updated RTT: 703.689µs (σ: 351.844µs)

[codecov]

Codecov Report

Merging #3071 (4e1cca5) into master (3b916f2) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3071      +/-   ##
==========================================
- Coverage   86.06%   86.05%   -0.01%     
==========================================
  Files         133      133              
  Lines        9441     9440       -1     
==========================================
- Hits         8125     8123       -2     
- Misses        954      955       +1     
  Partials      362      362              

Impacted Files	Coverage Δ
session.go	76.60% <ø> (-0.02%)	⬇️
internal/utils/rand.go	62.50% <0.00%> (-12.50%)	⬇️

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