Update project immutable.js to 3.0.3

libgrabber updated project immutable.js to 3.0.3.

@facebook

### Metadata information

```json
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    "name": "immutable.js",
    "repo": "facebook/immutable-js",
    "files": {
      "basePath": "dist/",
      "include": ["immutable.min.js", "immutable.d.ts"],
      "exclude": []
    },
    "path": "/home/jsdelivr/files/immutable.js",
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    "branchVersions": []
  },
  "version": "3.0.3",
  "updated": true,
  "updatePath": "/home/jsdelivr/files/immutable.js/3.0.3",
  "branch": "immutable.js/3.0.3"
}
```