Use single quotation marks

Author: jl-wynen

.github/workflows/pr_and_main.yml

@@ -64,14 +64,14 @@ jobs:
           python -m sphinx -j2 -v -b html -d doctrees docs html
           python -m sphinx -j2 -v -b doctest -d doctrees docs html
           find html -type f -name "*.ipynb" -not -path "html/_sources/*" -delete
-        if: ${{ contains(matrix.variant.os, 'ubuntu') && matrix.python-version == "3.8" }}
+        if: ${{ contains(matrix.variant.os, 'ubuntu') && matrix.python-version == '3.8' }}
 
       - run: python -m sphinx -j4 -v -b linkcheck -d doctrees docs html
         # Linkcheck can be flaky. Avoid randomly breaking PR builds by running only on `main`
-        if: ${{ contains(matrix.os, 'ubuntu') && matrix.python-version == "3.8" && github.ref == 'refs/heads/main' }}
+        if: ${{ contains(matrix.os, 'ubuntu') && matrix.python-version == '3.8' && github.ref == 'refs/heads/main' }}
 
       - uses: actions/upload-artifact@v2
-        if: ${{ contains(matrix.os, 'ubuntu') && matrix.python-version == "3.8" }}
+        if: ${{ contains(matrix.os, 'ubuntu') && matrix.python-version == '3.8' }}
         with:
           name: DocumentationHTML
           path: html/