[SPARK-35425][BUILD] Pin jinja2 in spark-rm/Dockerfile and add as a…

… required dependency in the release README.md

### What changes were proposed in this pull request?

The following two things are done in this PR.

* Add note about Jinja2 as a required dependency for document build.
* Add Jinja2 dependency for the document build to `spark-rm/Dockerfile`

### Why are the changes needed?

SPARK-35375(apache#32509) confined the version of Jinja to <3.0.0.
So it's good to note about it in `docs/README.md` and add the dependency to `spark-rm/Dockerfile`.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

I confimed that `make html` succeed under `python/docs` with the following command.
```
sudo pip install 'sphinx<3.1.0' mkdocs numpy pydata_sphinx_theme ipython nbsphinx numpydoc 'jinja2<3.0.0'
```

Closes apache#32573 from sarutak/required-module-for-python-doc.

Authored-by: Kousuke Saruta <sarutak@oss.nttdata.com>
Signed-off-by: Kousuke Saruta <sarutak@oss.nttdata.com>

dev/create-release/spark-rm/Dockerfile

@@ -40,7 +40,9 @@ ARG APT_INSTALL="apt-get install --no-install-recommends -y"
 # TODO(SPARK-32407): Sphinx 3.1+ does not correctly index nested classes.
 #   See also https://github.com/sphinx-doc/sphinx/issues/7551.
 #   We should use the latest Sphinx version once this is fixed.
-ARG PIP_PKGS="sphinx==3.0.4 mkdocs==1.1.2 numpy==1.19.4 pydata_sphinx_theme==0.4.1 ipython==7.19.0 nbsphinx==0.8.0 numpydoc==1.1.0"
+# TODO(SPARK-35375): Jinja2 3.0.0+ causes error when building with Sphinx.
+#   See also https://issues.apache.org/jira/browse/SPARK-35375.
+ARG PIP_PKGS="sphinx==3.0.4 mkdocs==1.1.2 numpy==1.19.4 pydata_sphinx_theme==0.4.1 ipython==7.19.0 nbsphinx==0.8.0 numpydoc==1.1.0 jinja2==2.11.3"
 ARG GEM_PKGS="bundler:2.2.9"
 
 # Install extra needed repos and refresh.

docs/README.md

@@ -67,10 +67,13 @@ To generate API docs for any language, you'll need to install these libraries:
 <!--
 TODO(SPARK-32407): Sphinx 3.1+ does not correctly index nested classes.
 See also https://github.com/sphinx-doc/sphinx/issues/7551.
+
+TODO(SPARK-35375): Jinja2 3.0.0+ causes error when building with Sphinx.
+See also https://issues.apache.org/jira/browse/SPARK-35375.
 -->
 
 ```sh
-$ sudo pip install 'sphinx<3.1.0' mkdocs numpy pydata_sphinx_theme ipython nbsphinx numpydoc
+$ sudo pip install 'sphinx<3.1.0' mkdocs numpy pydata_sphinx_theme ipython nbsphinx numpydoc 'jinja2<3.0.0'
 ```
 
 ## Generating the Documentation HTML