Fix oracle_specs table null value error

[AnExsomnis]

protocol upgrade failed for the data-nodes on the n00.testnet.vega.rocks:

Jul 20 16:18:21 n00.testnet.vega.xyz visor[3596010]: 2023-07-20T16:18:21.459Z        INFO        datanode.start.persistentPre.db-migrate        v3@v3.6.1/migration_sql.go:32        Rollback transaction
Jul 20 16:18:21 n00.testnet.vega.xyz visor[3596010]: 2023-07-20T16:18:21.460Z        ERROR        datanode.start.persistentPre        start/node_pre.go:136        Failed to initialise database, retrying...        {"error": "failed to migrate to latest schema:error migrating sql schema: ERROR 0004_oracle_specs.sql: failed to run SQL migration: failed to execute SQL query \"ALTER TABLE oracle_specs ADD COLUMN data JSONB NOT NULL;\\n\": ERROR: column \"data\" of relation \"oracle_specs\" contains null values (SQLSTATE 23502)"}
Jul 20 16:18:21 n00.testnet.vega.xyz visor[3596010]: 2023-07-20T16:18:21.460Z        INFO        datanode.start.persistentPre        start/node_pre.go:138        Database initialised