[4.2.x] Refs #34140 -- Made minor edits to rst code-blocks.

Backport of 9cf2a5df70 from main

docs/topics/performance.txt

@@ -120,9 +120,13 @@ do them faster than the template language can::
     # of the Python objects
     len(my_bicycles)
 
-    # Django template filter
-    # slower still, because it will have to count them in Python anyway,
-    # and because of template language overheads
+.. code-block:: html+django
+
+    <!--
+    Django template filter
+    slower still, because it will have to count them in Python anyway,
+    and because of template language overheads
+    -->
     {{ my_bicycles|length }}
 
 Generally speaking, the most appropriate level for the job is the lowest-level

docs/topics/testing/tools.txt

@@ -254,7 +254,9 @@ Use the ``django.test.Client`` class to make requests.
 
             /login/
 
-        ...with this POST data::
+        ...with this POST data:
+
+        .. code-block:: text
 
             name=fred&passwd=secret