Remove the 'akas' column and tidy up the documents for aws_backup_job table

[khushboo9024]

Integration test logs

Logs

``` Add passing integration test logs here ```

Example query results

Results

``` Add example SQL query results here (please include the input queries as well) ```

[misraved]

@khushboo9024 could you please fix the formatting in table_aws_backup_job.go file?

[misraved]

The akas column has been removed since the API does not return an ARN for this resource.

Reference doc - https://docs.aws.amazon.com/aws-backup/latest/devguide/API_BackupJob.html