fix(logging): Downgrade hash mismatch log level to info

[sentry]

The event_grouping_info.hash_mismatch condition was being logged at error level. This condition occurs when the grouping configuration for a project changes after an event has been ingested, leading to a discrepancy between the stored event hashes and the hashes recalculated on-the-fly for the grouping info API endpoint.

This is an expected and informational state, not an actual error, as the recalculation is done for display purposes and does not guarantee a match with historical data. Logging this as an error was causing significant noise in Sentry (over 300k occurrences).

This change downgrades the log level from error to info in _check_for_mismatched_hashes within src/sentry/grouping/grouping_info.py. The event_grouping_info.hash_mismatch metric will continue to be incremented, ensuring that the occurrence of these mismatches is still tracked, but they will no longer generate Sentry error events.

Legal Boilerplate

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Fixes SENTRY-RS9

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