Bump kinto from 13.6.3 to 13.6.4

Bumps [kinto](https://github.com/Kinto/kinto) from 13.6.3 to 13.6.4.
- [Release notes](https://github.com/Kinto/kinto/releases)
- [Changelog](https://github.com/Kinto/kinto/blob/master/CHANGELOG.rst)
- [Commits](Kinto/kinto@13.6.3...13.6.4)

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

requirements.txt

@@ -13,7 +13,7 @@ iso8601==0.1.12
 jsonpatch==1.25
 jsonpointer==2.0
 jsonschema==3.2.0
-kinto==13.6.3
+kinto==13.6.4
 logging-color-formatter==1.0.2
 PasteDeploy==2.1.0
 plaster==1.0