[BitBucket] Replace fstring with format function. (atlassian-api#830)

Author: Spacetown

atlassian/bitbucket/__init__.py

@@ -2638,7 +2638,7 @@ def download_repo_archive(
         :param prefix: string: Optional, a prefix to apply to all entries in the streamed archive; if the supplied prefix does not end with a trailing /, one will be added automatically
         :param chunk_size: int: Optional, download chunk size. Defeault is 128
         """
-        url = f"{self._url_repo(project_key, repository_slug)}/archive"
+        url = "{}/archive".format(self._url_repo(project_key, repository_slug))
         params = {}
         if at is not None:
             params["at"] = at