Use bcrypt rather than crypt in simple_server example

[cjwatson]

crypt was removed from Python 3.13. bcrypt isn't ideal, but it has acceptable password hashing, is simple to use, and is already an optional dependency of asyncssh.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.82%. Comparing base (fab96ac) to head (32a7d72).
Report is 77 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #697      +/-   ##
===========================================
- Coverage    99.85%   99.82%   -0.04%     
===========================================
  Files           95      101       +6     
  Lines        27784    29559    +1775     
  Branches      2908     3117     +209     
===========================================
+ Hits         27743    29506    +1763     
- Misses          38       47       +9     
- Partials         3        6       +3     

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[ronf]

Thanks for this, Colin!

As you said, bcrypt isn't ideal here but it's probably simpler than most other alternatives. This was meant to be a working example which included basic password validation, but I don't really expect someone to use this example in production code.