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

docs/topics/forms/index.txt

@@ -226,8 +226,8 @@ The :class:`Form` class
 We already know what we want our HTML form to look like. Our starting point for
 it in Django is this:
 
-.. snippet::
-    :filename: forms.py
+.. code-block:: python
+    :caption: forms.py
 
     from django import forms
 
@@ -276,8 +276,8 @@ logic.
 To handle the form we need to instantiate it in the view for the URL where we
 want it to be published:
 
-.. snippet::
-    :filename: views.py
+.. code-block:: python
+    :caption: views.py
 
     from django.http import HttpResponseRedirect
     from django.shortcuts import render
@@ -404,8 +404,8 @@ More on fields
 Consider a more useful form than our minimal example above, which we could use
 to implement "contact me" functionality on a personal website:
 
-.. snippet::
-    :filename: forms.py
+.. code-block:: python
+    :caption: forms.py
 
     from django import forms
 
@@ -453,8 +453,8 @@ values to a Python ``int`` and ``float`` respectively.
 
 Here's how the form data could be processed in the view that handles this form:
 
-.. snippet::
-    :filename: views.py
+.. code-block:: python
+    :caption: views.py
 
     from django.core.mail import send_mail