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] <[email protected]>

requirements.txt

@@ -14,7 +14,7 @@ click==8.0.2
 decorator==4.4.2
 Flask==1.1.2
 flower==1.2.0
-future==0.18.2
+future==0.18.3
 google-auth==1.16.1
 humanize==0.5.1
 idna==2.9