[Fix] Fix the model statistics in doc for readthedoc

[Junjun2016]

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Motivation

Fix the model statistics in doc for readthedoc

Modification

docs/en/stat.py
docs/zh_cn/stat.py

BC-breaking (Optional)

Does the modification introduce changes that break the backward-compatibility of the downstream repos?
No

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 MMDet3D.
4. The documentation has been modified accordingly, like docstring or example tutorials.