Adjust sentinel config directory permission to proactively prepare fo…

…r pebble v1.15

src/sentinel.py

@@ -134,7 +134,7 @@ def _copy_file(self, path: str, rendered: str, container: str) -> None:
             container.make_dir(
                 CONFIG_DIR,
                 make_parents=True,
-                permissions=0o770,
+                permissions=0o750,
                 user="redis",
                 group="redis",
             )