docs: fix typo in serve comment (contruct -> construct)

[mvanhorn]

Description

Fix a small typo in a code comment in src/borg/archiver/__init__.py
that describes the REST server backend handling: "contruct" -> "construct".

Comment-only change, no behavior change.

Checklist

• PR is against master
• New code has tests and docs where appropriate (comment-only typo fix, none needed)
• Commit messages are clean and reference related issues

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.09%. Comparing base (cc098ec) to head (f59258e).
⚠️ Report is 14 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #9860      +/-   ##
==========================================
+ Coverage   85.08%   85.09%   +0.01%     
==========================================
  Files          93       93              
  Lines       15436    15436              
  Branches     2332     2332              
==========================================
+ Hits        13134    13136       +2     
+ Misses       1603     1602       -1     
+ Partials      699      698       -1     

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[mvanhorn]

Appreciate you merging the typo fix, @ThomasWaldmann.

[ThomasWaldmann]

@mvanhorn Thanks for fixing it!

[mvanhorn]

Happy to help, and thanks for the fast merge @ThomasWaldmann!