Bump jsonschema from 3.0.2 to 3.1.1

Bumps [jsonschema](https://github.com/Julian/jsonschema) from 3.0.2 to 3.1.1.
- [Release notes](https://github.com/Julian/jsonschema/releases)
- [Changelog](https://github.com/Julian/jsonschema/blob/master/CHANGELOG.rst)
- [Commits](python-jsonschema/jsonschema@v3.0.2...v3.1.1)

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

requirements.txt

@@ -12,7 +12,7 @@ idna==2.8
 iso8601==0.1.12
 jsonpatch==1.24
 jsonpointer==2.0
-jsonschema==3.0.2
+jsonschema==3.1.1
 kinto==13.5.0
 logging-color-formatter==1.0.2
 PasteDeploy==2.0.1