chore: Remove dev SQL statement

Author: ditatompel

internal/database/schema.go

@@ -261,13 +261,10 @@ func v3(db *DB) error {
 	slog.Debug("[DB] Migrating database schema version 3")
 
 	// table: tbl_node
-	// TODO: Remove IF NOT EXISTS SQL statement below after merging to main
-	// branch. The statement only to accomodate commit 518d4b4 so future main
-	// branch keep on schema version 3.
 	slog.Debug("[DB] Adding additional columns to tbl_node")
 	_, err := db.Exec(`
 		ALTER TABLE tbl_node
-		ADD COLUMN IF NOT EXISTS ipv6_only TINYINT(1) UNSIGNED NOT NULL DEFAULT '0' AFTER cors_capable,
+		ADD COLUMN ipv6_only TINYINT(1) UNSIGNED NOT NULL DEFAULT '0' AFTER cors_capable,
 		ADD COLUMN ip_addresses TEXT NOT NULL DEFAULT '' AFTER cors_capable;`)
 	if err != nil {
 		return err