chore(django_docutils) Fix redundant cast

src/django_docutils/template.py:71: error: Redundant cast to "str"  [redundant-cast]
Found 1 error in 1 file (checked 55 source files)

src/django_docutils/template.py

@@ -68,7 +68,7 @@ def render(
             context["csrf_token"] = csrf_token_lazy(request)
         context = {"source": self.source, "writer_name": "html"}
 
-        return mark_safe(t.cast("str", core.publish_parts(**context)["html_body"]))
+        return mark_safe(core.publish_parts(**context)["html_body"])
 
 
 register_pygments_directive()