Fix mypy error code 'import-untyped'

Author: schnellerhase

pyproject.toml

@@ -91,7 +91,6 @@ disable_error_code = [
     "assignment",
     "attr-defined",
     "import-not-found",
-    "import-untyped",
     "method-assign",
     "misc",
     "operator",

ufl/mathfunctions.py

@@ -421,7 +421,7 @@ def evaluate(self, x, mapping, component, index_values):
         """Evaluate."""
         a = self.ufl_operands[1].evaluate(x, mapping, component, index_values)
         try:
-            import scipy.special
+            import scipy.special  # type: ignore
         except ImportError:
             raise ValueError(
                 "You must have scipy installed to evaluate bessel functions in python."