Docs: Update to jinja2<3.2, Dependabot admonitions versions <3.1.4 (#528)

## About
What the title says.

## Details
It's only about building static docs, so there is no danger for this
project. It's just a chore fix to properly dismiss the security warning
signalled by Dependabot.

## References
- https://github.com/kennethreitz/responder/security/dependabot/61

Author: kennethreitz

docs/requirements.txt

@@ -1,5 +1,5 @@
 alabaster<0.8
-jinja2<2.11
+jinja2<3.2
 markupsafe<2
 readme-renderer<23
 sphinx>=5,<6