Source S3: add defaults to file types to fix spec CATs

[clnoll]

What

Fixes the spec CAT by adding a default key to the expected output (in spec.json).

[github-actions]

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[clnoll]

@bazarnov I'm not sure why this test started failing suddenly when the same version had just passed. Did we upgrade airbyte-cdk's pydantic version recently? At any rate this should fix it.

cc @brianjlai - this PR is related to the old spec, but since it follows the pattern of the v4 spec that you've been involved with I thought you might have some insight into it.

[octavia-squidington-iii]

source-s3 test report (commit e022a7070f) - ✅

⏲️ Total pipeline duration: 17mn22s

Step	Result
Validate airbyte-integrations/connectors/source-s3/metadata.yaml	✅
Connector version semver check	✅
QA checks	✅
Code format checks	✅
Connector package install	✅
Build source-s3 docker image for platform linux/x86_64	✅
Unit tests	✅
Integration tests	✅
Acceptance tests	✅

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