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

docs/ref/contrib/admin/index.txt

@@ -2929,8 +2929,8 @@ instantiate any other Python class) and register your models and
 ``ModelAdmin`` subclasses with it instead of with the default site. Finally,
 update :file:`myproject/urls.py` to reference your :class:`AdminSite` subclass.
 
-.. snippet::
-    :filename: myapp/admin.py
+.. code-block:: python
+    :caption: myapp/admin.py
 
     from django.contrib.admin import AdminSite
 
@@ -2943,8 +2943,8 @@ update :file:`myproject/urls.py` to reference your :class:`AdminSite` subclass.
     admin_site.register(MyModel)
 
 
-.. snippet::
-    :filename: myproject/urls.py
+.. code-block:: python
+    :caption: myproject/urls.py
 
     from django.urls import path
 
@@ -2972,24 +2972,24 @@ You can override the default ``django.contrib.admin.site`` by setting the
 to the dotted import path of either a ``AdminSite`` subclass or a callable that
 returns a site instance.
 
-.. snippet::
-    :filename: myproject/admin.py
+.. code-block:: python
+    :caption: myproject/admin.py
 
     from django.contrib import admin
 
     class MyAdminSite(admin.AdminSite):
         ...
 
-.. snippet::
-    :filename: myproject/apps.py
+.. code-block:: python
+    :caption: myproject/apps.py
 
     from django.contrib.admin.apps import AdminConfig
 
     class MyAdminConfig(AdminConfig):
         default_site = 'myproject.admin.MyAdminSite'
 
-.. snippet::
-    :filename: myproject/settings.py
+.. code-block:: python
+    :caption: myproject/settings.py
 
     INSTALLED_APPS = [
         ...

docs/ref/contrib/admin/javascript.txt

@@ -31,8 +31,8 @@ In your custom ``change_form.html`` template, extend the
     <script type="text/javascript" src="{% static 'app/formset_handlers.js' %}"></script>
     {% endblock %}
 
-.. snippet:: javascript
-    :filename: app/static/app/formset_handlers.js
+.. code-block:: javascript
+    :caption: app/static/app/formset_handlers.js
 
     (function($) {
         $(document).on('formset:added', function(event, $row, formsetName) {
@@ -69,8 +69,8 @@ namespace, just listen to the event triggered from there. For example:
     <script type="text/javascript" src="{% static 'app/unregistered_handlers.js' %}"></script>
     {% endblock %}
 
-.. snippet:: javascript
-    :filename: app/static/app/unregistered_handlers.js
+.. code-block:: javascript
+    :caption: app/static/app/unregistered_handlers.js
 
     django.jQuery(document).on('formset:added', function(event, $row, formsetName) {
         // Row added