Bump flake8-docstrings from 1.3.0 to 1.3.1 in /{{cookiecutter.app_name}} (#532)

Bumps [flake8-docstrings](https://gitlab.com/pycqa/flake8-docstrings) from 1.3.0 to 1.3.1.
- [Release notes](https://gitlab.com/pycqa/flake8-docstrings/tags)
- [Changelog](https://gitlab.com/pycqa/flake8-docstrings/blob/master/HISTORY.rst)
- [Commits](https://gitlab.com/pycqa/flake8-docstrings/commits/master)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

{{cookiecutter.app_name}}/Pipfile

@@ -53,7 +53,7 @@ black = "==19.3b0"
 flake8 = "==3.7.8"
 flake8-blind-except = "==0.1.1"
 flake8-debugger = "==3.1.0"
-flake8-docstrings = "==1.3.0"
+flake8-docstrings = "==1.3.1"
 pydocstyle = "<4" #temporary until flake8-docstrings is fixed
 flake8-isort = "==2.7.0"
 isort = "==4.3.21"