Change the default setting of the Augmentation feature flag

The augmentation feature was added to OSDU indexer since M18. It was protected by the feature flag index-augmenter-enabled. By default, it is OFF.

Given the following the following facts:

• The augmentation is driven by augmentation configurations deployed to Storage service, the feature won't take effect even it is turned ON when there is no augmentation configuration deployed.
• SLB has enabled this FF for some of its clients in the testing and production environment since M20. The feature is being used everyday now. No severe side-effect was reported, such as slowdown of the indexer and search service, causing corruption of the index and etc..
• To enable the augmentation feature which is managed via Partition Service, it requires special privilege that only service providers have normally. It is counter-productive for the service providers to enable it per data partition when this feature has been proved to be useful and reliable.

In this MR, we change the default status of the augmentation feature from OFF to ON. The service providers still can turn it off using the Partition Service if the feature is not desirable for certain clients.