Address CI failures

[khaeru]

1. In the "pytest" workflow, TestISTAT.test_gh_104(): the query of https://esploradati.istat.it/SDMXWS/rest/data/22_289/.IT..1+2.TOTAL.99 is returning a 404 error with the text/plain content:

   Error while retrieving Mappings from "Mapping Store"! Cause:Dataflow 'urn:sdmx:org.sdmx.infomodel.datastructure.Dataflow=IT1:22_289(1.0)' doesn't contain a mapping set

   Despite the response code, this appears to be more of a 500 Internal Server Error → mark as Xfail

2. In the "sources" CI workflow, the "collect" job was not correctly updated in Fix read of str:Categorisation > str:Target from SDMX-ML 2.1 #215 to use uv run python ….

PR checklist

• Checks all ✅
• Update documentation N/A, CI changes only
• Update doc/whatsnew.rst

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.88%. Comparing base (2accc1c) to head (b3a8e53).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #216      +/-   ##
==========================================
+ Coverage   98.03%   98.88%   +0.85%     
==========================================
  Files          98       98              
  Lines        8231     8232       +1     
==========================================
+ Hits         8069     8140      +71     
+ Misses        162       92      -70     

Files with missing lines	Coverage Δ
sdmx/tests/test_sources.py	96.69% <100.00%> (+3.33%)	⬆️

... and 18 files with indirect coverage changes