JSON Decoder error in local run of Manifest

During a local run of the manifest file, the following error was experienced:
```
weather_dl/download_pipeline/manifest.py", line 228, in _update
manifest = json.load(file)
...
json.decoder.JSONDecodeError: Expecting ',' delimiter: line 1 column 609980 (char 609979)
```

## Workaround
- Changing the directory for the local run and re-running fixed the issue.