[Storage][JellyfishMerkle] Use Self when possible
[Storage][JellyfishMerkle] Use Self when possible

Closes: #1726
Approved by: lightmark

aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core