Fix bug in convert_coco_format

[ImJaewooChoi]

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Motivation

For a simple test, I ran the instance segmentation demo.ipynb, but encountered a problem in the convert_balloon_to_coco function. By fixing this error, i hope to avoid confusion for beginners using mmdetection.

Modification

Previously, using the convert_balloon_to_coco function resulted in the following error.

TypeError: "tasks" must be a tuple object or a sequence object, but got <class 'dict_values'>

To fix this, I changed the type to list.

The changes are as follows:
data_infos.values() --> list(data_infos.values())

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repos?
If so, please describe how it breaks the compatibility and how the downstream projects should modify their code to keep compatibility with this PR.

Use cases (Optional)

If this PR introduces a new feature, it is better to list some use cases here, and update the documentation.

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDet or MMPreTrain.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[ImJaewooChoi]

@hhaAndroid @RangiLyu could you check my PR?