Minor cleanup for s3-csv-reader

[alecgard]

• Return the LastModifed time of the S3 object as providerIndicatedTimeUnixMs.
• Tweak config description and re-generate README

Steps to Test

1. Integ tests
2. Unit tests

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: b063101c87edbd92252e05b34ff257a688a067e1

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | -------------------------------- | ----- | | @chainlink/s3-csv-reader-adapter | Minor |

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