use file -b --mime 'test.json' have problem in AWS linux 2

[calos0921]

We use the AWS linux2 image and to run file -b --mime 'test.json'
result: text/plain; charset=us-ascii.

So we use application/json and text/plain to resolve the problem.
validates_attachment :file, content_type: { content_type: ['application/json', 'text/plain'] }