Install altair when testing

.github/workflows/build_test.yml

@@ -299,7 +299,7 @@ jobs:
           python -m pip install polars-lts-cpu "duckdb>=1.0" "vl-convert-python>=1.0.1rc1" scikit-image "pandas>=2.2" jupytext voila anywidget ipywidgets chromedriver-binary-auto
 
           # Test dependencies
-          python -m pip install pytest vega-datasets scikit-image jupytext voila ipykernel anywidget ipywidgets selenium flaky tenacity chromedriver-binary-auto 
+          python -m pip install pytest altair vega-datasets scikit-image jupytext voila ipykernel anywidget ipywidgets selenium flaky tenacity chromedriver-binary-auto 
       - name: Test lazy imports
         working-directory: python/vegafusion/
         run: python checks/check_lazy_imports.py
@@ -347,7 +347,7 @@ jobs:
           python -m pip install polars "duckdb>=1.0" vl-convert-python "pandas>=2.2"
 
           # Test dependencies
-          python -m pip install pytest vega-datasets scikit-image
+          python -m pip install pytest altair vega-datasets scikit-image
 
       - name: Test vegafusion
         working-directory: python/vegafusion/
@@ -392,7 +392,7 @@ jobs:
           python -m pip install pyarrow==10.0 altair==5.1.2 polars[timezone] "duckdb>=1.0" vl-convert-python 
           
           # Test dependencies
-          python -m pip install pytest vega-datasets scikit-image
+          python -m pip install pytest altair vega-datasets scikit-image
       - name: Test vegafusion
         working-directory: python/vegafusion/
         run: pytest --ignore=tests/test_altair_mocks.py