Bump ipython from 2.3.1 to 7.16.3 in /requirements

Bumps [ipython](https://github.com/ipython/ipython) from 2.3.1 to 7.16.3.
- [Release notes](https://github.com/ipython/ipython/releases)
- [Commits](https://github.com/ipython/ipython/compare/rel-2.3.1...7.16.3)

---
updated-dependencies:
- dependency-name: ipython
  dependency-type: direct:development
...

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

requirements/dev-requirements.txt

@@ -1,5 +1,5 @@
 -r test-requirements.txt
 django-debug-toolbar==1.2.2
 ipdb==0.8
-ipython==2.3.1
+ipython==7.16.3
 pygraphviz==1.2