Fix v_num formatting for RichProgressBar (#21040)

Author: SkafteNicki

src/lightning/pytorch/callbacks/progress/rich_progress.py

@@ -184,7 +184,7 @@ def render(self, task: "Task") -> Text:
 
         def _generate_metrics_texts(self) -> Generator[str, None, None]:
             for name, value in self._metrics.items():
-                if not isinstance(value, str):
+                if not isinstance(value, (str, int)):
                     value = f"{value:{self._metrics_format}}"
                 yield f"{name}: {value}"