Use case-insensitive comparison in dashboard sync logic

[ABZhang0]

Related command

az grafana dashboard sync

General Guidelines

• [x] Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• [x] Have you run python scripts/ci/test_index.py -q locally? (pip install wheel==0.30.0 required)
• [x] My extension version conforms to the Extension version schema

[azure-client-tools-bot-prd[bot]]

️✔️Azure CLI Extensions Breaking Change Test

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️✔️Non Breaking Changes

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[yonzhan]

Thank you for your contribution! We will review the pull request and get back to you soon.

[github-actions[bot]]

For more info about extension versioning, please refer to Extension version schema

[azclibot]

[Release] Update index.json for extension [ amg ] : https://dev.azure.com/azclitools/release/_build/results?buildId=163315&view=results