Bump django-formtools from 2.1 to 2.2

Bumps [django-formtools](https://github.com/jazzband/django-formtools) from 2.1 to 2.2.
- [Release notes](https://github.com/jazzband/django-formtools/releases)
- [Changelog](https://github.com/jazzband/django-formtools/blob/master/docs/changelog.rst)
- [Commits](jazzband/django-formtools@2.1...2.2)

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

requirements.txt

@@ -3,4 +3,4 @@ Django==1.11.26 # pyup: <2.0
 django-debug-toolbar==2.1
 docutils==0.15.2
 freezegun==0.3.12
-django-formtools==2.1
+django-formtools==2.2