Bump docutils from 0.17.1 to 0.18

Bumps [docutils](http://docutils.sourceforge.net/) from 0.17.1 to 0.18.

---
updated-dependencies:
- dependency-name: docutils
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

requirements.txt

@@ -1,6 +1,6 @@
 coverage==6.0.2
 Django==2.2.24
 django-debug-toolbar==3.2.2
-docutils==0.17.1
+docutils==0.18
 freezegun==1.1.0
 django-formtools==2.3