fix format_lazy typing (#2504)

Author: ashm-dev

django-stubs/utils/text.pyi

@@ -59,4 +59,4 @@ def unescape_string_literal(s: _StrOrPromiseT) -> _StrOrPromiseT: ...
 def slugify(value: _StrOrPromiseT, allow_unicode: bool = False) -> _StrOrPromiseT: ...
 def camel_case_to_spaces(value: str) -> str: ...
 
-format_lazy: Callable[..., str]
+format_lazy: Callable[..., _StrOrPromise]