Apply X | Y type hints style for asyncssh/sk.py

[waketzheng]

Description

The code was automatically changed by running ruff check --select=UP --fix asyncssh/sk.py with Ruff version 0.16.1.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.84%. Comparing base (fab96ac) to head (0f78f57).
⚠️ Report is 213 commits behind head on develop.

Additional details and impacted files

@@ Coverage Diff @@## develop #825 +/- ##
===========================================
- Coverage 99.85% 99.84% -0.02% 
===========================================
Files 95 102 +7 Lines 27784 32149 +4365 Branches 2908 3113 +205 ===========================================
+ Hits 27743 32098 +4355 - Misses 38 45 +7 - Partials 3 6 +3 

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[ronf]

Now that the minimum supported version of Python for AsyncSSH has moved to 3.10, migrating to this new syntax is an option, and definitely something I'd consider.

That said, I appreciate your effort, but instead of opening a PR I would suggest opening a discussion thread with suggestions for what tool and arguments can be used to do the automated conversion (like you included in this PR). I'd have to do a line-by-line validation anyway that the tool didn't affect anything other than typing information, and I'd have more confidence doing that when running such a tool first-hand.

This applies to any automated formatting or syntax upgrading.