Update jinja2 requirement from <3.0 to <4.0

Updates the requirements on [jinja2](https://github.com/pallets/jinja) to permit the latest version.
- [Release notes](https://github.com/pallets/jinja/releases)
- [Changelog](https://github.com/pallets/jinja/blob/main/CHANGES.rst)
- [Commits](pallets/jinja@2.0rc1...3.0.1)

---
updated-dependencies:
- dependency-name: jinja2
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements-dev.txt

@@ -5,6 +5,6 @@ sphinxcontrib-fulltoc==1.2.0
 nbsphinx==0.7.1
 
 # https://github.com/pydata/xarray/issues/5299#issuecomment-840730954
-jinja2<3.0
+jinja2<4.0
 
 -r ./requirements-test.txt