Remove 2nd client hello post openssl 1.1.1 bug workaround

[CoolCat467]

In this pull request, we remove a workaround for a bug in OpenSSL 1.1.1 with DTLS ClientHellos being eaten. There is a comment noting that it should be safe to remove this workaround in 2024 or so, so the time is neigh!

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 99.58%. Comparing base (af010af) to head (914b9e8). Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3097      +/-   ##
==========================================
- Coverage   99.58%   99.58%   -0.01%     
==========================================
  Files         121      121              
  Lines       18167    18166       -1     
  Branches     3268     3268              
==========================================
- Hits        18092    18091       -1     
  Misses         52       52              
  Partials       23       23              

Files with missing lines	Coverage Δ
src/trio/_dtls.py	97.50% <ø> (-0.01%)	:arrow_down:

[jakkdl]

ubuntu 18.06, as mentioned in the comment, reached EOL at 2023-05-31. So yeah I'm guessing it'll be fine

[CoolCat467]

Going to merge this soon unless anyone has any additional concerns, consensus seems to be that removing duplicate should be fine.