Update sync_dist warning for multiple processes (#6790)

Author: kaushikb11

pytorch_lightning/trainer/connectors/logger_connector/epoch_result_store.py

@@ -133,8 +133,8 @@ def run_epoch_func(self, results, opt_metric, func_name, *args, **kwargs) -> Non
                         warning_cache.warn(
                             f"The value associated to the key {non_metric_key}: {metric.cpu().tolist()} "
                             "doesn't appear to be the same accross all processes. "
-                            "HINT: One could either do: `self.log(..., sync_dist=True, sync_fn=torch.mean)`"
-                            " to force mean reduction across processes which can be inaccurate or implement"
+                            "HINT: One could either do: `self.log(..., sync_dist=True)` to force mean"
+                            " reduction by default across processes which can be inaccurate or implement"
                             " a `torchmetrics.Metric`"
                         )
                     warning_cache.warned_metrics.append(non_metric_key)