Update docs build to Python 3.11. Fix a few warnings.

.readthedocs.yaml

@@ -8,7 +8,7 @@ version: 2
 build:
   os: ubuntu-20.04
   tools:
-    python: "3.9"
+    python: "3.11"
 
 # Build documentation in the docs/ directory with Sphinx
 sphinx:

docs/attribution/0001-analytics.rst

@@ -384,7 +384,7 @@ link element.
 
 
 Product Downloads
-~~~~~~~~~~~~~~~~
+~~~~~~~~~~~~~~~~~
 
 .. Important::
 

docs/redirects.rst

@@ -212,7 +212,7 @@ and to it you can add both a ``product`` and ``campaign`` query parameter. For
 example, the following URL would redirect to either Firefox on the Apple App Store
 or on the Google Play Store, with the specified campaign parameter.
 
-.. code_block::
+.. code-block::
 
     https://www.mozilla.org/firefox/browsers/mobile/app/?product=firefox&campaign=firefox-whatsnew