This was accidentally introduced in D15545, so we remove it again.
Removing it solves a few problems:
- OP_RETURN can't be spent, so having them in the UTXO DB is incorrect.
- These scripts can't be compressed very well, increasing the DB size disproportionally.
- The scripthash -> script index (for ElectrumX) is already tens of gigabytes; removing OP_RETURNs contributes to reducing this index.
If users want OP_RETURNs to be indexed, it is probably a Chronik plugin they want (which can color OP_RETURNs, and even parse the OP_RETURN), and since plugins are strictly more powerful than a simple OP_RETURN index, there's no actual need to have this indexed.