fix(clickhouse): Fix timestamp precision

[jdenquin]

This pull request focuses on optimizing timestamp precision in the unique_count_query.rb file by adjusting the precision level in various SQL queries. The changes include modifying the toDateTime64 function to use a precision of 3 instead of 5 across different methods.

Timestamp precision adjustments:

• app/services/events/stores/clickhouse/unique_count_query.rb: Changed the precision in the events_cte_sql method to use timestamp directly instead of toDateTime64(timestamp, 5, 'UTC').
• app/services/events/stores/clickhouse/unique_count_query.rb: Updated the grouped_events_cte_sql method to use timestamp directly instead of toDateTime64(timestamp, 5, 'UTC').
• app/services/events/stores/clickhouse/unique_count_query.rb: Modified the period_ratio_sql method to use toDateTime64 with a precision of 3 instead of 5 for the from_datetime and to_datetime parameters.
• app/services/events/stores/clickhouse/unique_count_query.rb: Adjusted the grouped_period_ratio_sql method to use toDateTime64 with a precision of 3 instead of 5 for the from_datetime and to_datetime parameters.