Bump future from 0.18.2 to 0.18.3

Bumps [future](https://github.com/PythonCharmers/python-future) from 0.18.2 to 0.18.3.
- [Release notes](https://github.com/PythonCharmers/python-future/releases)
- [Changelog](https://github.com/PythonCharmers/python-future/blob/master/docs/changelog.rst)
- [Commits](PythonCharmers/python-future@v0.18.2...v0.18.3)

---
updated-dependencies:
- dependency-name: future
  dependency-type: direct:production
...

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

requirements.txt

@@ -12,7 +12,7 @@ Flask==1.1.4
 https://github.com/mozilla-iam/Flask-pyoidc/archive/v1.0.0.tar.gz
 Flask-SSLify==0.1.5
 funcsigs==1.0.2
-future==0.18.2
+future==0.18.3
 gunicorn==20.1.0
 idna==2.10
 ipaddress==1.0.23