fix: rightsize and switch instance to graviton

[infracost-fixer]

Infracost created this pull request, see issue details here

Update the Terraform resource used to generate arn:aws:rds:us-east-1:1234:db:drone-rds

Action: Rightsize
Current Configuration: db.m5.xlarge
Recommended Configuration: db.m6g.xlarge
Risk: High
Potential Monthly Savings: $55.18

The following tags in the code were used to map the AWS recommendation to aws_db_instance.drone

{
 "Name": "drone",
 "app": "drone"
}

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