chore: remove clickhouse migration comments

Mono-RevId: 3aebd3f66589db879b18fd669c91f81bb7eb8df3

Author: carderne

internal-packages/clickhouse/schema/042_reduce_task_events_v2_storage_overhead.sql

@@ -1,7 +1,5 @@
 -- +goose Up
 
--- Full-text search is served outside the source event table. Keeping these
--- indexes here adds work to every event insert and merge without serving reads.
 ALTER TABLE trigger_dev.task_events_v2
     DROP INDEX IF EXISTS idx_attributes_text_search,
     DROP INDEX IF EXISTS idx_attributes_text,