The aws_ami data source is intended for declaring a dependency on exactly one external AMI. It does not support returning multiple AMIs.
The hashicorp/aws provider has a separate data source aws_ami_ids which can return the IDs of zero or more AMIs matching given criteria.
However, retrieving all AMIs owned by amazon may not be a sufficient filter for useful behavior because owner alone is typically not a sufficient discriminator for finding AMIs that provide particular functionality. The owners argument is primarily intended to use in conjunction with other filters to avoid selecting AMIs with other owners that might have similar naming schemes.