Support for SSH-1.99 SSH Identification String from Client

[Jayson-Fong]

This change addresses #777 by dropping the self.is_client() condition when checking for SSH-1.99 in the protoversion, thereby allowing it to apply to both client and server instances.

asyncssh/asyncssh/connection.py

Lines 1553 to 1554 in d281290

	if (version.startswith(b'SSH-2.0-') or
	(self.is_client() and version.startswith(b'SSH-1.99-'))):

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.83%. Comparing base (fab96ac) to head (e76d276).
⚠️ Report is 152 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #778      +/-   ##
===========================================
- Coverage    99.85%   99.83%   -0.02%     
===========================================
  Files           95      100       +5     
  Lines        27784    31552    +3768     
  Branches      2908     3036     +128     
===========================================
+ Hits         27743    31501    +3758     
- Misses          38       45       +7     
- Partials         3        6       +3     

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[ronf]

Given that RFC 4253 is nearly 20 years old at this point, I don't know how much value there is in continuing to support SSH 1.99 as an identification string. However, I don't see any real harm in it, so I've gone ahead and merged this change in the AsyncSSH "develop" branch. Thanks for your PR!