Fix wrong size of mask in RTMDet-Ins post-processing

[flytocc]

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Motivation

Please describe the motivation of this PR and the goal you want to achieve through this PR.

Fix wrong size of mask in rtmdet-ins post-processing. #2580 open-mmlab/mmdetection#11230

Modification

Please briefly describe what modification is made in this PR.

reverse the width and height in scale_factor

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 tests to ensure the correctness.
3. If the modification has a dependency on downstream projects of a newer version, this PR should be tested with all supported versions of downstream projects.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[RunningLeon]

LGTM