Bump pip-tools from 4.3.0 to 4.4.0 (#18)

Bumps [pip-tools](https://github.com/jazzband/pip-tools) from 4.3.0 to 4.4.0.
- [Release notes](https://github.com/jazzband/pip-tools/releases)
- [Changelog](https://github.com/jazzband/pip-tools/blob/master/CHANGELOG.md)
- [Commits](jazzband/pip-tools@4.3.0...4.4.0)

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

requirements-dev.txt

@@ -29,7 +29,7 @@ mypy-extensions==0.4.3    # via mypy
 mypy==0.761
 packaging==19.2           # via pytest, tox
 pathspec==0.6.0           # via black
-pip-tools==4.3.0
+pip-tools==4.4.0
 pkginfo==1.5.0.1          # via twine
 pluggy==0.13.1            # via pytest, tox
 py==1.8.0                 # via pytest, tox