Rename cf_database_96 to cf_database (it's not at version 9.6.x anymore)

[jfredrickson5]

In order to reduce confusion about what PostgreSQL version is in use, we want the RDS module to be named cf_database instead of cf_database_96. The database engine was previously version 9.6.x. At this time, the database is at version 12.x. See here.

Acceptance Criteria

• GIVEN after module has been renamed
  WHEN we run a terraform plan and terraform apply
  THEN Terraform does not recognize the rename as an infrastructure change
  AND the infrastructure is unaffected by the rename

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Security considerations

None since it is a simple Terraform module rename.

Implementation sketch

Seems like this might require a terraform state mv.