qvm-ls: Remove 3.x compatibility and update manpage

[hippalectryon-0]

Major

• Remove 3.x compatibility interfaces
• Improve / Update manpage

Minor

• Remove --spinner argument (which is the default)
• Minor cleanup (unused code comments, typos)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.78%. Comparing base (1a623d1) to head (b5729df).
⚠️ Report is 66 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #443      +/-   ##
==========================================
+ Coverage   76.24%   76.78%   +0.53%     
==========================================
  Files          53       53              
  Lines        9322     9363      +41     
==========================================
+ Hits         7108     7189      +81     
+ Misses       2214     2174      -40     

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