fix: fix the absence of matching synonyms during category insight import

[raphael0202]

• use create_taxonomy_mapping from SDK
• use taxonomy_mapping for categories to match the canonical ID

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 2 lines in your changes missing coverage. Please review.

Project coverage is 55.54%. Comparing base (fb6c5dc) to head (424796f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
robotoff/insights/importer.py	83.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1497      +/-   ##
==========================================
- Coverage   55.56%   55.54%   -0.02%     
==========================================
  Files          85       85              
  Lines        8739     8740       +1     
==========================================
- Hits         4856     4855       -1     
- Misses       3883     3885       +2     

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