ModelCheckpointCallback is triggered by mistake after every validation stage when mannual optimization

@lantiga is already working on this.

Since Dec 4, 2024.

### Bug description

I set the every_n_epochs param of ModelCheckpoint to 1 and val_check_interval of trainer to 200. The total iter of a batch is 1000. It should not save checkpoint files after the val_check. But it does.

### What version are you seeing the problem on?

v2.4

### How to reproduce the bug

_No response_

### Error messages and logs

```
# Error messages and logs here please
```

### Environment

Current environment

```
#- PyTorch Lightning Version (e.g., 2.4.0):
#- PyTorch Version (e.g., 2.4):
#- Python version (e.g., 3.12):
#- OS (e.g., Linux):
#- CUDA/cuDNN version:
#- GPU models and configuration:
#- How you installed Lightning(`conda`, `pip`, source):
```

### More info

_No response_

cc @tchaton @justusschock @awaelchli @borda