BUG: mypy: ignore the file in mypy.ini

This adds the file `scipy/_lib/_uarray/_backend.py` to the ignore
lists in `mypy.ini` as mypy 0.770 detects a syntax error (on Python
3.9.0a5) which cannot be ignored via directives like `# type: ignore`.

Author: tirthasheshpatel

mypy.ini

@@ -385,6 +385,9 @@ ignore_errors = True
 [mypy-scipy.spatial.tests.test_distance]
 ignore_errors = True
 
+[mypy-scipy._lib._uarray._backend]
+ignore_errors = True
+
 #
 # Files referencing compiled code that needs stubs added.
 #

scipy/_lib/_uarray/_backend.py

@@ -93,7 +93,7 @@ def generate_multimethod(
     argument_extractor: ArgumentExtractorType,
     argument_replacer: ArgumentReplacerType,
     domain: str,
-    default: typing.Optional[typing.Callable] = None,  # type: ignore
+    default: typing.Optional[typing.Callable] = None,
 ):
     """
     Generates a multimethod.