Tweak mypy runner for internal mypy error

Context: https://github.com/python/mypy/issues/17396

run-mypy.sh

@@ -4,4 +4,4 @@ set -ex
 
 mypy --show-error-codes pytools
 
-mypy --strict --follow-imports=skip pytools/datatable.py pytools/persistent_dict.py
+mypy --strict --follow-imports=silent pytools/datatable.py pytools/persistent_dict.py