Fix logging error on SIGHUP

changelog.d/14258.bugfix

@@ -0,0 +1,2 @@
+Fix a bug introduced in Synapse 1.60.0 which caused an error to be logged when Synapse received a SIGHUP signal, and debug logging was enabled.
+

synapse/app/_base.py

@@ -558,7 +558,7 @@ def reload_cache_config(config: HomeServerConfig) -> None:
             logger.warning(f)
     else:
         logger.debug(
-            "New cache config. Was:\n %s\nNow:\n",
+            "New cache config. Was:\n %s\nNow:\n %s",
             previous_cache_config.__dict__,
             config.caches.__dict__,
         )