Refs #20910 -- Replaced snippet directive with code-block.

docs/ref/models/expressions.txt

@@ -314,8 +314,8 @@ The ``Func`` API is as follows:
         ``arg_joiner``, and any other ``**extra_context`` parameters to
         customize the SQL as needed. For example:
 
-        .. snippet::
-            :filename: django/db/models/functions.py
+        .. code-block:: python
+            :caption: django/db/models/functions.py
 
             class ConcatPair(Func):
                 ...

docs/ref/models/fields.txt

@@ -1194,8 +1194,8 @@ Relationships defined this way on :ref:`abstract models
 <abstract-base-classes>` are resolved when the model is subclassed as a
 concrete model and are not relative to the abstract model's ``app_label``:
 
-.. snippet::
-    :filename: products/models.py
+.. code-block:: python
+    :caption: products/models.py
 
     from django.db import models
 
@@ -1205,8 +1205,8 @@ concrete model and are not relative to the abstract model's ``app_label``:
         class Meta:
             abstract = True
 
-.. snippet::
-    :filename: production/models.py
+.. code-block:: python
+    :caption: production/models.py
 
     from django.db import models
     from products.models import AbstractCar