ci(typing): Adds scipy-stubs to altair[doc]

`scipy` is only used for one example in the user guide, but this will be the second https://docs.scipy.org/doc/scipy/release/1.15.0-notes.html#other-changes
vega · mattijn · Jan 18, 2025 · Feb 26, 2018 · Jan 4, 2025 · Jan 4, 2025
commit dc7639d4a41baf3a476403238c1d970927ba352f
diff --git a/pyproject.toml b/pyproject.toml
@@ -96,7 +96,7 @@ doc = [
     "myst-parser",
     "sphinx_copybutton",
     "sphinx-design",
-    "scipy",
+    "scipy-stubs[scipy]",
 ]
 
 [tool.hatch.version]