remove extra cursor from update zimfarm task function

[Best2Two]

I was exploring the codebase, and I found an extra cursor that was being opened unnecessarily. I believe it is redundant and should be removed.

[audiodude]

Nice catch!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.78%. Comparing base (93efe8e) to head (9a560b7).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1131      +/-   ##
==========================================
- Coverage   92.78%   92.78%   -0.01%     
==========================================
  Files          74       74              
  Lines        4312     4311       -1     
==========================================
- Hits         4001     4000       -1     
  Misses        311      311              

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