Apply suggested fix to tna_utilities/api.py from Copilot Autofix

Co-authored-by: Copilot Autofix powered by AI <223894421+github-code-quality[bot]@users.noreply.github.com>

Author: ahosgood

tna_utilities/api.py

@@ -159,7 +159,7 @@ def _handle_response(self, response: Response) -> dict:
                 error_body = response.text
             raise Exception(f"Bad request for URL '{response.url}': {error_body}")
         if response.status_code == 401:
-            raise ResourceUnauthorized("Unauthorised")
+            raise ResourceUnauthorized("Unauthorized")
         if response.status_code == 403:
             raise ResourceForbidden("Forbidden")
         if response.status_code == 404: