store: remove redundant index

pkg/connector/store/upgrades/00-latest.sql

@@ -1,4 +1,4 @@
--- v0 -> v4 (compatible with v2+): Latest revision
+-- v0 -> v5 (compatible with v2+): Latest revision
 
 CREATE TABLE telegram_user_state (
     user_id BIGINT NOT NULL PRIMARY KEY,
@@ -16,8 +16,6 @@ CREATE TABLE telegram_channel_state (
     PRIMARY KEY (user_id, channel_id)
 );
 
-CREATE INDEX telegram_channel_state_user_id_idx ON telegram_channel_state (user_id);
-
 CREATE TABLE telegram_access_hash (
     user_id     BIGINT NOT NULL,
     entity_type TEXT   NOT NULL,

pkg/connector/store/upgrades/05-remove-redundant-index.sql

@@ -0,0 +1,2 @@
+-- v5 (compatible with v2+): Remove redundant index on telegram_channel_state
+DROP INDEX telegram_channel_state_user_id_idx;