set NUMBA_THREADING_LAYER=omp in Matlab CI job (to avoid failures with default TBB threading) (#1747)

Author: slayoo

.github/workflows/readme_snippets.yml

@@ -65,6 +65,9 @@ jobs:
       - uses: actions/setup-python@v5.0.0
         with:
           python-version: "3.12"
+
+      - run: echo NUMBA_THREADING_LAYER=omp >> $GITHUB_ENV
+
       - run: pip install -e .
       - run: pip install pytest-codeblocks pytest
       - run: python -c "import pytest_codeblocks; code=pytest_codeblocks.extract_from_file('docs/markdown/pysdm_landing.md'); f=open('readme.m', 'w'); f.writelines(block.code for block in code if block.syntax=='Matlab'); f.close()"