rabbit_feature_flags: Fix logging of the list of feature flags

"~~" was ok when the final string was a format string, but it's not
anymore. We need a simple "~".

Author: dumbbell

deps/rabbit/src/rabbit_ff_registry_factory.erl

@@ -396,7 +396,7 @@ do_initialize_registry(RegistryVsn,
            "Feature flags:   [~ts] ~ts~n",
            [case maps:get(FeatureName, FeatureStates, false) of
                 true           -> "x";
-                state_changing -> "~~";
+                state_changing -> "~";
                 false          -> " "
             end,
             FeatureName])