fix the getting started documentation error

[thinkthinking]

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Motivation

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

Modification

there is a error in getting-start doc, config file is misspelling

BC-breaking (Optional)

Does the modification introduce changes that break the back-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.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[CLAassistant]

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[ZCMax]

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[OpenMMLab-Assistant005]

Dear thinkthinking,
First of all, we want to express our gratitude for your significant PR in the MMDet3D project. Your contribution is highly appreciated, and we are grateful for your efforts in helping improve this open-source project during your personal time. We believe that many developers will benefit from your PR.
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Thank you again for your contribution❤
Best regards！ @thinkthinking