[camera] set useAutoFocus to true by default

[markfili]

Description

There's no way to set Camera for Android's useAutoFocus property to true and it is false by default so auto focusing is not working in preview mode. This change sets the useAutoFocus property to true by default because the changes in the related pull request (flutter#3383) prior to this one ensures the check for auto focus capability and handles it accordingly.

Related Issues

Follow-up patch for flutter/flutter#73160

Checklist

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Breaking Change

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