Update docstring in html.py (#6279)

The explanation of 'sources' is inadequate especially because this is probably going to be most used with `LinkContentFetcher` that returns `List[ByteStream]`

haystack/preview/components/file_converters/html.py

@@ -29,7 +29,7 @@ def run(self, sources: List[Union[str, Path, ByteStream]]):
         """
         Converts a list of HTML files to Documents.
 
-        :param sources: Paths to HTML files.
+        :param sources: List of HTML file paths or ByteStream objects.
         :return: List of converted Documents.
         """
         documents = []