fix: simplify Flyway migration for address_utxo index creation

Remove conditional check for index existence in migration script.
Flyway handles migration idempotency, so the explicit IF NOT EXISTS
check is unnecessary and can be simplified to a direct CREATE INDEX.

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Co-Authored-By: Claude <noreply@anthropic.com>

Author: 2 people

yaci-indexer/src/main/resources/db/store/postgresql/V1.0_900_0__rosetta_app_addres_utxo.sql

@@ -1,11 +1 @@
-DO $$
-BEGIN
-    IF NOT EXISTS (
-        SELECT 1 FROM pg_indexes
-        WHERE indexname = 'idx_address_utxo_tx_hash'
-        AND tablename = 'address_utxo'
-        AND schemaname = current_schema()
-    ) THEN
-        CREATE INDEX idx_address_utxo_tx_hash ON address_utxo USING btree (tx_hash);
-    END IF;
-END $$;
+CREATE INDEX idx_address_utxo_tx_hash ON address_utxo USING btree (tx_hash);