➖ Remove jinja2 dependency (#861)

- This was explicitly pinned for breaking changes in `readthedocs`.
- `readthedocs` manages this dependency on its own.

requirements/requirements_dev.txt

@@ -2,7 +2,6 @@
 -r ../docs/requirements.txt
 coverage>=7.0.0
 docutils>=0.18.1
-jinja2>=3.0.3, <3.1.0
 mypy>=1.6.1
 pip>=22.3
 poetry-bumpversion>=0.3.1