[1.5.x] Fixed #19714 -- Updated documentation about TemplateView context

Thanks Aramgutang for the report. Refs #17228.
Backport of 56e553129 from master.

docs/ref/class-based-views/base.txt

@@ -101,8 +101,13 @@ TemplateView
 
 .. class:: django.views.generic.base.TemplateView
 
-    Renders a given template, passing it a ``{{ params }}`` template variable,
-    which is a dictionary of the parameters captured in the URL.
+    Renders a given template, with the context containing parameters captured
+    in the URL.
+
+    .. versionchanged:: 1.5
+        The context used to be populated with a ``{{ params }}`` dictionary of
+        the parameters captured in the URL. Now those parameters are first-level
+        context variables.
 
     **Ancestors (MRO)**