remove non-functioning 0-RTT test with different conn ID lengths

[marten-seemann]

This test was introduced in #3058.

[codecov]

Codecov Report

Merging #3079 (4efe5f5) into master (5a3fd58) will increase coverage by 0.14%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3079      +/-   ##
==========================================
+ Coverage   86.04%   86.18%   +0.14%     
==========================================
  Files         132      130       -2     
  Lines        9435     9358      -77     
==========================================
- Hits         8118     8065      -53     
+ Misses        955      937      -18     
+ Partials      362      356       -6     

Impacted Files	Coverage Δ
packet_handler_map.go	73.30% <0.00%> (-0.97%)	⬇️
internal/qtls/go116.go
conn_ecn.go

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