Make cache error log more readable

lib/pleroma/web/plugs/http_signature_plug.ex

@@ -104,7 +104,9 @@ defp maybe_require_signature(
           :noop
 
         any ->
-          Logger.warn("expected request signature cache to run, got #{any}")
+          Logger.warn(
+            "expected request signature cache to return a boolean, instead got #{inspect(any)}"
+          )
       end
     end