[SPARK-40552][BUILD][INFRA] Upgrade protobuf-python to 4.21.6

### What changes were proposed in this pull request?
Upgrade protobuf-python from 4.21.5 to 4.21.6
[Release notes](https://github.com/protocolbuffers/protobuf/releases/tag/v21.6)

### Why are the changes needed?
[CVE-2022-1941](https://nvd.nist.gov/vuln/detail/CVE-2022-1941)
and
[Github](GHSA-8gq9-2x98-w8hf)

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
Pass GA

Closes #37991 from bjornjorgensen/protobuf4.21.6.

Authored-by: Bjørn <bjornjorgensen@gmail.com>
Signed-off-by: Sean Owen <srowen@gmail.com>

dev/create-release/spark-rm/Dockerfile

@@ -42,7 +42,7 @@ ARG APT_INSTALL="apt-get install --no-install-recommends -y"
 #   We should use the latest Sphinx version once this is fixed.
 # 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 twine==3.4.1 sphinx-plotly-directive==0.1.3 pandas==1.1.5 pyarrow==3.0.0 plotly==5.4.0 markupsafe==2.0.1 docutils<0.17 grpcio==1.48.1 protobuf==4.21.5"
+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 twine==3.4.1 sphinx-plotly-directive==0.1.3 pandas==1.1.5 pyarrow==3.0.0 plotly==5.4.0 markupsafe==2.0.1 docutils<0.17 grpcio==1.48.1 protobuf==4.21.6"
 ARG GEM_PKGS="bundler:2.2.9"
 
 # Install extra needed repos and refresh.

dev/requirements.txt

@@ -48,4 +48,4 @@ black==22.6.0
 
 # Spark Connect
 grpcio==1.48.1
-protobuf==4.21.5
+protobuf==4.21.6