add internal keyword to SettingsDialog

[lyh990517]

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What I have done and why

The Internal keyword was added to settingDialog, which is only referenced inside the module.
It seems there is no need to use it externally.

How I'm testing it

I simply built and ran it.

Do tests pass?

• Run local tests on DemoDebug variant: ./gradlew testDemoDebug
• Check formatting: ./gradlew --init-script gradle/init.gradle.kts spotlessApply

Is this your first pull request?

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• Run ./tools/setup.sh
• Import the code formatting style as explained in the setup script.

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