Fixed broken links in class based views flattend index; refs #24250.

docs/ref/class-based-views/flattened-index.txt

@@ -168,7 +168,7 @@ FormView
 * :meth:`~django.views.generic.edit.FormMixin.form_invalid`
 * :meth:`~django.views.generic.edit.FormMixin.form_valid`
 * :meth:`~django.views.generic.edit.ProcessFormView.get`
-* :meth:`~django.views.generic.edit.FormMixin.get_context_data`
+* :meth:`~django.views.generic.base.ContextMixin.get_context_data`
 * :meth:`~django.views.generic.edit.FormMixin.get_form`
 * :meth:`~django.views.generic.edit.FormMixin.get_form_kwargs`
 * :meth:`~django.views.generic.base.View.http_method_not_allowed`
@@ -207,7 +207,7 @@ CreateView
 * :meth:`~django.views.generic.edit.FormMixin.form_invalid`
 * :meth:`~django.views.generic.edit.FormMixin.form_valid`
 * :meth:`~django.views.generic.edit.ProcessFormView.get`
-* :meth:`~django.views.generic.edit.FormMixin.get_context_data`
+* :meth:`~django.views.generic.base.ContextMixin.get_context_data`
 * :meth:`~django.views.generic.edit.FormMixin.get_form`
 * :meth:`~django.views.generic.edit.FormMixin.get_form_kwargs`
 * :meth:`~django.views.generic.detail.SingleObjectMixin.get_object`
@@ -249,7 +249,7 @@ UpdateView
 * :meth:`~django.views.generic.edit.FormMixin.form_invalid`
 * :meth:`~django.views.generic.edit.FormMixin.form_valid`
 * :meth:`~django.views.generic.edit.ProcessFormView.get`
-* :meth:`~django.views.generic.edit.FormMixin.get_context_data`
+* :meth:`~django.views.generic.base.ContextMixin.get_context_data`
 * :meth:`~django.views.generic.edit.FormMixin.get_form`
 * :meth:`~django.views.generic.edit.FormMixin.get_form_kwargs`
 * :meth:`~django.views.generic.detail.SingleObjectMixin.get_object`