Update PR template from tox to black-nb

.github/PULL_REQUEST_TEMPLATE.md

@@ -11,6 +11,6 @@ _Put an `x` in the boxes that apply. You can also fill these out after creating
 - [ ] I have read the [CONTRIBUTING](https://github.com/aws/amazon-sagemaker-examples/blob/master/CONTRIBUTING.md) doc and adhered to the example notebook best practices
 - [ ] I have updated any necessary documentation, including [READMEs](https://github.com/aws/amazon-sagemaker-examples/blob/master/README.md)
 - [ ] I have tested my notebook(s) and ensured it runs end-to-end
-- [ ] I have linted my notebook(s) and code using `tox -e black-format,black-nb-format`
+- [ ] I have linted my notebook(s) and code using `black-nb -l 100 {path}/{notebook-name}.ipynb`
 
 By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.